A/N Hey everybody! I'm so excited right now! I have been planning this story for literally MONTHS. It's a Carlos whump/angst and it kind of goes in fashion with Mystery of You. Whenever I first joined this fandom, I had planned on doing a mystery illness fic for each one of the boys, it's just taken me a really long time do so. But here's the next fic in my little "series" I guess you could say! This time, though, Carlos' illness is MUCH more complicated and difficult, so I have been doing endless research. Hopefully I get as much facts as I can right! But this story is like, my favorite one and really close to my heart so I REALLY hope you all enjoy it, and I have it all mapped out and planned for finishing, (I know I have a terrible habit of being ADHD and flighty and not finishing stories. I'm sorry… They will all be finished one day teehee)

So, without further ado, here is chapter one of "Deteriorate." Please enjoy

"Happy Birthday to you, Happy Birthday to you! Happy Birthday dear Carlos, Happy Birthday to you!"

A smile twitched upon Carlos' peaceful face as James' words floated into the sleeping boy's dreams. James grinned at this and sang the song again, this time succeeding in waking his best friend from his slumber.

"James?" Carlos groaned, smiling at the pleasant alarm James had given him. The small Latino scrubbed his eyes with the back of his hands, rubbing the groggy feeling away. It was his birthday today! He was ready to be hyper and crazy and eat food and cake with his friends all day.

"Happy Birthday buddy!" James yelled out with enthusiasm. He flung his arms around the small boy's body and squeezed, lifting him easily into the air. "How old are you today? 14, 15?" James teased. He loved poking fun at Carlos for looking way younger than he really was. Besides the fact that Carlos was only 5 feet, 5 inches inches tall, his rosy, chubby cheeks and innocent features made him look much younger than he really was. James found it all too endearing.

"I'm 18!" Carlos said, rolling his eyes. He had been teased by James his whole life for "never growing up." He rolled out of James' arms, stood up, and brushed himself off. "When's the party, James? There's going to be a party, right?"

"Duh!" James said, ruffling the younger boy's hair. "Pool party this afternoon, and yours truly will be doing the bbq'n."

Carlos grinned with excitement. He loved parties, especially birthday parties, and since they only came once a year, they only made him even giddier.

"Hop on little bro!" James said, patting his own back. "Logan is making birthday pancakes!"

"Oh yes!" Carlos exclaimed, his mouth watering with the thought of Logan's famous birthday pancakes slathered in syrup. He had to stand on top of his bed so he could attach himself to James' back, since the brunette was so much taller than him, and James carried him to the kitchen.

"Hey James, do you think maybe now that I'm 18 I might grow a little bit?" Carlos wondered.

"I don't know," James said, hoisting Carlos higher up on his back when he started to slide down. Carlos wrapped his legs around his waist and hugged his neck tightly, making James smile. "I kind of like that you're little, anyway. Oh darlin' don't you ever grow up, don't you ever grow up just stay this little!" James suddenly belted, making Carlos blush.

"I have to grow up someday James," Carlos said. "I can't be tiny forever."

"Sure you can!" James said. "You're Carlitos, the baby of the brothers of the ice. You're just not meant to grow anymore, buddy."

Carlos pouted at this, but only for a moment. His bubbliness was back when he saw Logan cooking up chocolate pancakes, and Kendall sitting at the table with some presents piled up.

"Pancakes! Presents!" Carlos cried out, not sure where to start first. He slid off of James' back and looked from Logan to Kendall, conflicted.

"Hey Carlos, Happy Birthday!" Kendall said, getting up from the table to give his little buddy a huge hug.

"Thanks Kendall!" Carlos said. He ran to Logan next, who laughed and gave him a bear hug.

"Good morning Carlos, Happy Birthday!" Logan said. "Pancakes will be ready in a minute, go open your presents!'

Carlos made an odd sound of happiness and punched the air. He ran to the table and tore open the first present he saw.

"That one's from all of us," Kendall said, watching Carlos brown eyes light up with joy.

"Whoa! This is the skateboard I've been wanting!" Carlos cried out, holding up the green and black board for his friends to see, even though they were the ones who bought it for him.

"Whoa, pretty cool Carlos!" James said, nodding.

"Me and helmet love it!" Carlos said. He dug into the rest of his presents, which were violent video games and clothes he had been wanting.

After opening presents, Carlos shoveled 7 pancakes into his mouth greedily, savoring the melty chocolate chips that Logan had put in them.

"Can I have some more?" Carlos asked, barely finished chewing the pancake he already had in his mouth.

"Nope, I'm cutting you off," Logan said. "You'll get a stomachache. Besides, James is going to be cooking up burgers in a few hours and you want to be hungry for those."

"Ok," Carlos said. "I'm going to go get dressed and practice some tricks on my new skateboard!"

"Be careful," Logan warned. "You don't want to break anything on your birthday. And don't forget helmet!" Logan added, wondering why he even bothered to remind Carlos to wear something that was constantly on his head anyway. But sometimes Carlos had a habit of being weird and not wearing his helmet when he needed it most.

After Carlos showered, spiked his hair, and dressed in his new birthday outfit, which was a red checkered shirt and dark wash blue jeans, he headed down to the park to show off his new skateboard and perform some tricks for his friends while Kendall, James and Logan decorated the pool deck for their best friend's very special day.

A few hours later, when everything was decorated, Logan went down to the park to go pick up Carlos and tell him the party was set to start in a few minutes. He was pretty impressed to find Carlos doing all kinds of ollies and small tricks on his new board.

"Hey Carlos, you're getting really good at that," Logan said after a few minutes of watching his friend skate back and forth.

Carlos turned around and grinned shyly. "Thanks, Logan! Want to watch me do a trick?"

"Sure, watcha got?" Logan said, sitting on a bench to watch the show.

"I'm going to grind that rail," Carlos said, pointing to a concrete staircase about 20 feet away. It was only 5 steps, but still, it looked too dangerous for Logan's liking.

"Oh, I don't know about that," Logan said, eyeing the rail warily. If Carlos wiped out, he could cause some serious damage.

"Don't worry, I've done it like, 10 times already today!" Carlos said. "This board rocks! It's way faster than my old one. Thanks Logan!"

"You're welcome buddy, but I just don't know about grinding rails," Logan said.

"It'll be fine, just watch!" Carlos said. Logan sighed when Carlos ignored his protests and started skating off towards the railing.

Logan gripped the green park bench and gritted his teeth as Carlos hopped onto the rail. A surge of panic went through him as Carlos slid down the rail. He braced himself to go running to help Carlos for the bad landing that he feared might happen.

Carlos' board came to the end of the rail at lightning speed and he flew into the air. Logan yelled out his name on reflex as he imagined his friend crashing to the ground. Logan shut his eyes tight, refusing to watch an accident happen.

"Logan! Logan!" Carlos cried. Logan cringed, preparing himself to hear cries and wails of pain. But instead, Carlos sounded… Happy?

"Logie, did you see me?" Carlos asked.

Logan opened his eyes to see Carlos had landed perfectly on his board, on 2 feet and not his face, and was now dancing around happily. Logan let out a sigh of relief and grinned.

"Wow, Carlos that was really good!" Logan praised, still feeling kind of shaky from watching his friend dart down a railing like that. He had seen enough reality shows to know bad things happened to skaters, but Carlos' skill and balance was amazing.

"Why did you get so worried?" Carlos asked as they walked back to the apartment.

"You know I'm a worry wart Carlos," Logan said. Carlos nodded, barely hearing him. He was too distracted by the already huge gathering by the pool, with balloons and a huge banner saying "Happy Birthday Carlos!" and not to mention lots of food, and the firepit going.

"Logan it's awesome!" Carlos said, completely breathless as he was engulfed by hugs and pats on the backs while a swarm of friends wished him Happy Birthday.

The next couple of hours went by quickly, spent swimming and goofing off and playing pool games. Music blared off the speakers, while Mr. Bitter's hid in absolute misery. Carlos was actually pretty sure that someone had to have kidnapped him and tied him up to allow such a party, not that Carlos was complaining. It was the best Birthday Party he ever had. Even the Jennifer's had shown up and planted kisses to his cheek as a present.

"James, are the burgers ready yet?" Carlos asked, bounding over to where his best friend stood at the BBQ, cooking up hamburgers. All of that swimming and mingling had made him starving.

"Almost, about 10 more minutes," James said, flipping the burgers. "They aren't quite well done yet,"

"I don't even care," Carlos said dramatically. "I am so hungry."

James rolled his eyes and tried to find the most done burger on the grill. "Ok, ok. Here you go Carlos," James said, plating up a burger and handing it to Carlos, who dug right in and went to the table of chips and salads to fill up his plate even more. James shook his head. He had never met anyone who was able to eat quite as much as Carlos could.

A few minutes later, everyone was seated around the pool eating burgers. Logan chuckled at Carlos, who was sitting next to him and still stuffing his face with all the goodies his friends had made.

"Dude you're gonna get sick," Logan warned. Carlos snorted.

"Quit being a worrywart, Logan!" Carlos teased, his mouth full of jello salad. Logan elbowed him in the ribs lightly at his remark.

After everyone was finished eating and evening drew in, Guitar Dude suggested a firepit jam. Carlos sat in the middle of the bench around the fire, sandwiched between Kendall and James. He curled his legs up under him and settled against the cushions, watching the sunset as his dozens of friend's belt out lyrics to their songs. Pinks and oranges swirled in with majestic purple hues in the sky as his friend's voices rang through the light breeze.

Carlos hugged his knees to his chest and sighed with contentment. He had never been happier in his life. He felt so… Loved. It was the greatest feeling he had ever known.

As soon as the sun was as low as it could go and the sky was dark, dusky twilight, everybody started clapping. Carlos twisted around in his seat to see what everyone was cheering for, and he saw Logan emerge from the lobby with a large chocolate birthday cake, covered in white frosting and sweet words and 19 tall, flickering candles (One extra candle being for good luck.)

Carlos stood up and felt his cheeks heat up as Logan sat the cake on a table and the crowd erupted into a very tone-deaf styling of "Happy Birthday."

"Happy Birthday Carlos," James whispered when the song was finished, giving his buddy a one armed hug. "Make a wish."

Carlos thought for a moment, wondering what in the world he could possibly need to wish for when everything was already so perfect. He looked around, puffing his cheek out. The young Latino was stumped.

"Make a wish already!" James said giddily, practically jumping up and down with excitement.

Carlos chuckled, deciding on the perfect wish. He took in a deep breath as everyone watched him expectantly, but right when he let out the burst of air, a strange pain resonated through his stomach, making him cringe. The puff of air was weak and hardly enough to blow out even half of the candles that were nearly halfway melted by now.

But as quickly as it came, the pain vanished. Carlos was confused, but decided to think nothing of it. Maybe he just took too large of a breath? Again, Carlos filled his cheeks with air and blew as hard as he could. The candles snuffed out with a "poof" and everyone started cheering wildly.

While Logan set to work on cutting the cake, Kendall started handing out small flute glasses filled with sparkling red grape juice, Carlos' favorite.

"I would like to purpose a toast, to my buddy!" Kendall said in a mock drunken slur, stumbling over to Carlos and draping a floppy arm across the smaller boy's shoulders. "Who is 18 years old today and still retaining every ounce of adorableness that we love him for." Kendall squeezed Carlos' cheek teasingly and smirked. "But really, this is one of the coolest guys I have ever known. He's crazy and amazing and I couldn't imagine life without my little buddy."

"Hear, hear!" James shouted, raising his glass. The crowd of Carlos' friends repeated James' words and held up their glasses as well.

"To Carlos, our best friend, and our little brother," Logan said fondly.

Just as everyone was about to clink glasses with the person next to them, Carlos interrupted them.

"Hold on, hold on," Carlos said, sticking his hand up like a school child. "Can I add something?"

"Go ahead buddy!" Logan said, and everyone turned their attention to the birthday boy. Carlos blushed, feeling shy under the smiles of his friends, who gave him their undivided attention. He cleared his throat nervously and started to speak.

"I just wanted to make this toast for something else, too. For my best friends Logan, Kendall and James, who aren't just my best friends, but my band mates, also. We get to experience something amazing called a world tour, and we leave next week, and I am still trying to wrap my mind around that. So I want to toast to our second album, our world tour, and Big Time Rush. I don't know what I would do without you guys. Cheers!"

"Cheers," Kendall whispered, giving Carlos a smile. He felt like he could tear up. The grin on Carlos' face was something that would be etched in his mind forever.

"Cheers!" Everyone shouted over Kendall, and the cool night air was filled with the sounds of clinking glasses. Carlos brought the glass to his lips and tilted his head back, swallowing the bubbly pink liquid. It felt cool and refreshing on his throat, but as soon as the cider hit his stomach, he was hit with a burst of nausea.

Carlos clutched his stomach and frowned at the sick feeling. He sat back down on the bench, feeling a bit weak. He looked around to make sure nobody noticed his sudden ailment, but the teenagers were engrossed in picking out slices of cake and thankfully did not see what was happening.

"And the biggest slice for Carlitos!" Logan said, turning around and presenting Carlos a particularly large slice of cake with several of those yummy frosting flowers that were his favorite.

"Thanks," Carlos said with lack-luster, and Logan noticed the sour look upon his soft features. The excited grin was wiped completely off his face.

"You ok?" Logan asked, wondering what could have upset his little friend so quickly.

"Mmhmm," Carlos answered, but Logan was worried when he set his piece of cake beside him untouched.

Logan sat next to Carlos and placed a hand on his back. "You don't want your cake?"

Carlos shook his head. "Maybe later, Logie. My… My tummy hurts all of a sudden." Carlos looked up at Logan sadly, and the brunette pouted in sympathy.

"You probably ate way too much, 'Litos. I knew that would happen. Just take it easy for a bit and you will be fine. No more eating."

Carlos exhaled and put a hand on his stomach. "I don't plan on it."

Logan offered Carlos a smile and squeezed his knee. "Let's play some games to get your mind off the tummyache," he offered, and Carlos nodded.

For the next hour, the large group of kids jammed out and played games and chatted. Carlos' stomachache did not get any better, though. The pain was only getting worse, and it seemed to be moving lower and lower.

"Is your stomach still bugging you buddy?" Logan asked, noticing that Carlos was not participating in the party at all anymore. In fact, he had not moved from the pillows lining the bench. He stared blankly at the fire, eyes glassy and arm wrapped around his middle. Logan felt terrible for Carlos. He couldn't even enjoy his own birthday party.

"Yeah, it hurts," Carlos whimpered with pain evident in his voice. His stomach cramped up and the boy groaned in misery. "Ah, ow. It hurts, Logan."

Logan was starting to worry that maybe Carlos' ailment wasn't just because he ate too much. He was starting to look pale and get the sweats, which wasn't normal. He feared that he was actually sick and not full.

"Come on Carlos let's go up to your room for a few minutes," Logan suggested, taking the smaller boy by his arm and pulling him to his feet.

"Why?" Carlos asked, sounding like a small child. He sniffled and looked around at his bustling, loud party sadly. "I don't want to Logan."

"I know buddy but I don't want you to throw up in front of your friends. The party will be going on for a few more hours. You'll feel better if you try to go to the bathroom and lie down for a bit."

Carlos nodded, his shoulders sagging forward. He didn't want to leave his party, but he knew Logan was right, and throwing up for everyone to see would not be very fun.

"Bye everyone," Carlos whispered, following behind Logan.

"Hey, where you guys going?" James asked, intercepting Logan when he saw him leading Carlos, who was hunched over and walking very slowly, towards the lobby. "'Litos are you ok?"

Carlos shook his head "no," and rubbed his stomach. "I don't feel very good."

James frowned and took Carlos into a gentle hug. "Oh no what happened?" He asked, looking to Logan for the answer because Carlos was too busy whimpering and moaning into his shirt to speak.

"He said his stomach hurts," Logan explained. "I thought at first it might be because he ate too much, but he seems to be in a lot of pain and it almost looks like he's running a fever, doesn't it?"

"He does feel warm," James commented, feeling a small amount of heat radiating off of Carlos' face and onto his chest. He rubbed Carlos' arms. The flesh was a bit heated. "You don't think he's sick, do you? Not on his birthday…" James felt instantly bad for Carlos. What a horrible way to spend a birthday.

"I don't know," Logan said somberly, gathering Carlos and putting an arm around him. "I'm going to take him upstairs now, let Kendall know what's going on. We'll be back in about an hour, I hope."

Carlos was unusually quiet on the way to the apartment. When they rode up the elevator, he paled and cringed, grabbing at the railings when intense vertigo washed over him. He was afraid he might even puke then and there.

"Logan I don't want to throw up," Carlos admitted as Logan opened the front door and escorted him inside their warm home.

"Well if it happens, it happens," Logan said. He brought Carlos to his room and laid him down on his fluffy comforter. Carlos curled up on his side into a tiny ball, his arms wrapped tightly around his middle.

"I am so sorry this is happening," Logan said, sitting beside his friend and feeling his forehead, which was definitely warm enough for a fever. "I think you have a temperature, I'll be right back." Logan fetched a thermometer from the bathroom and brought it back. Carlos scrunched up his face when he saw the device.

"Open up," Logan said. "The sooner I take your temperature, the sooner I can get you healthy so you can go back to the party."

Carlos found this reasonable and opened up his mouth for Logan to place it under his tongue. He pouted and whined when the metal tip jabbed into the bottom of his tongue. Logan rolled his eyes and mussed the boy's hair up.

"Ssh, it'll just take a minute."

It seemed like more than a minute to Carlos, but finally it beeped and Logan took it out and read the numbers aloud. "Ninety nine point four, not bad, but still it means you're sick. Does anything else hurt? Your head or your throat, maybe?"

"No," Carlos said. It was the truth. The only thing that was bothering him was his lower tummy.

"Hmm. Where does your stomach hurt?" Logan said, resting his hand on Carlos abdomen and pressing lightly. If Carlos really had eaten too much, his stomach would have been hard and extended, but it was still soft.

"Lower," Carlos said, and Logan pressed down on his stomach a couple inches downward, making Carlos groan in pain. Tears pricked at his eyes.

"Oh, sorry Carlos," Logan said quickly, trying to rub out the pain in his stomach. "Well, my guess is you ate something bad? Indigestion wouldn't cause a fever. But you ate the same things as we did today so I don't really understand."

"I just want it to stop hurting," Carlos whimpered. Logan rubbing his stomach was only helping a little bit. He was afraid of throwing up.

"It'll go away soon buddy, just rest for a bit and let it runs its course," Logan said. "Do you want some ginger ale?"

Carlos shook his head, burying his face in his pillow. The cramps were getting really bad now, causing his stomach to churn. He had never been so nauseated in his life.

"I have to go to the bathroom," Carlos mumbled, the stuffing in his pillow making his words sound more like "mmph umph uh mmphoom."

"What was that?" Logan asked, leaning forward so he could hear a little better.

Carlos turned his head slightly to the side and repeated himself. "I have to go to the bathroom."

"Oh, Oh!" Logan said with realization, helping Carlos to his feet. He led him to their shared bathroom. "Do you want me to come in with you?"

"Ok," Carlos said as he kneeled in front of the toilet. Logan sat on the edge of the tub and they waited. Carlos was gripping the toilet with white knuckles as wave after wave of pain washed over his tummy, but he never threw up.

"Logie," Carlos whined with rising frustration, looking to his friend for help with big, doe-like eyes that glistened with the beginnings of tears.

"Maybe you don't need to throw up yet," Logan said. "Do you want to lie down and I can bring you a bucket instead?"

Carlos nodded and shakily started to rise to his feet. He felt like he needed to lay down now.

Logan helped him up off the tile floor, but as soon he stood up straight, he felt an odd, uncomfortable and painful sensation in his lower abdomen.

"Carlos, are you alright?" Logan asked when the Latino's face distorted with the intense pain.

"No," Carlos whimpered, cringing. He shoved a perplexed Logan out the door and locked it just in time to get to the toilet and pull his jeans to his ankles.

"Carlos, are you ok?" Logan asked, pounding on the door, and Carlos kind of wished he would go away for the moment. If he wasn't in so much pain, he would have been embarrassed, but right now his stomach felt like it was being ripped apart.

Carlos cried out and shuddered, gripping his aching stomach. Finally he found the strength to answer his worried best friend. "I'm ok Logie just wait for me in my room."

Logan sighed and stopped knocking. "Ok, buddy. Call me if you need anything." The brunette went back to Carlos' room and sat on his bed, feeling anxious. He tried to think of something, anything, that could have made Carlos so violently ill but he could not recall his friend anything spoiled in the past couple of days.

A few minutes later, a very sweaty and pale Carlos trudged into the bedroom, his eyes half shut and arms around his stomach. He looked pitiful, and Logan's heart broke at the sight.

"What happened, 'Los?"

"I had diarrhea," Carlos admitted shyly. "But I didn't throw up. I feel like I need to but I can't."

"Oh, Carlos," Logan said softly. The younger boy crawled underneath the covers that Logan lifted for him and started to cry. He kept moaning "it hurts, it hurts," over and over again, until finally he fell asleep. Logan lied down next to Carlos and slung an arm around his shoulders, deciding he didn't feel safe leaving Carlos alone at the moment, and took out his cellphone.

"Carlos is too sick to come back to the party. Something is wrong," Logan texted to James. "I think he might have a touch of the flu. See you later tonight."

Logan pressed send and settled down into the pillows. Carlos' sweaty body curled into Logan's and clutched his waist as if he was a teddy bear, but the brunette didn't mind. He felt terrible for Carlos. His birthday had been ruined. Logan just hoped it wasn't anything too serious.

A/N Whew first chapter done! I hope you guys like it so far! What do you think? I'll be leaving little clues throughout the chapters over what's wrong with Carlos so keep your eyes peeled if you want to try to guess! Now I'm going to go work on the next chaps of Silence and Trapped because no, I haven't forgotten about those!

Thank you so much for reading, and reviews are my heartbeat! If you leave one, you will get cherry macaroons dipped in chocolate. Mmmm, tantalizing.