Author's Note: Writing this story- well it's definitely a personal thing for me because I've suffered from anxiety for a while now and I also have an OCD, so I really used my own experiences to write Sam here, and I hope I did okay. Also a warning for 3x16 spoilers.
Sam doesn't know when it started.
Okay that's a lie. It started when Dean made the deal, and in a way that made sense. Your brother makes a deal that costs him his life so of course you're going to end up worrying. Obsessing. That's normal, right?
Sam tries to convince himself that it's normal. This constant worry that clouds his mind and takes over his senses until he's cloaked in it, choking in its gossamer arms. But Sam's not stupid, Stanford education and all, and he eventually figures out that not being able to think, to function every time Dean gets into the Impala by himself and drives away to a bar or to get food, is definitely not normal.
It gets so bad that Dean starts noticing. Sam has one hand on his cell phone pressed up to his ear and is shocked when Dean questions him about the way he's been acting. Sam knows that something isn't right, but hearing Dean saying it to him brings him to a whole other kind of reality that he doesn't want to face.
"Dude what's wrong with you?" Dean's voice travels through phone.
Sam quirks an eyebrow, shrugging his shoulders though he knows Dean can't see him.
"What's wrong with me? There's nothing wrong with me. What are you talking about Dean?"
As he's talking Sam taps his fingers over his knee. Three times. It's a habit he's developed over the months. Ever since it started.
Sam waits for Dean to say something else, but he doesn't, and he's just too fucking weary to correct Dean, to say "It's Sam."
"Sammy, you call me all the time, you ask where I'm going every time I step out of the room. You're acting different. Look Sam is it the dea-"
Sam quickly cut Dean off. "Dean I'm fine. Just…just be careful."
"Yeah, okay. Bye."
Sam snapped the phone shut his brow furrowing. Frankly he was surprised that Dean had brought up his recent apprehension. He leaned back against the headboard, chewing his lip. Sam stared at the door of the hotel room, nervously tapping his fingers on his knee. 1, 2, 3. Over and over again until Dean finally stepped through the door and Sam could breathe again.
After the trickster, and the hundreds of Tuesdays, and that one horrifying Wednesday, and those long, cold months without Dean, Dean, Dean, Sam's worry has grown to swallow him whole. It eats at him, taking large bites and chewing slowly so that every time Dean isn't right there, right next to him, Sam worries. He worries all the time, even when he doesn't need to. If Dean spends too long in the bathroom Sam starts to feel that now familiar sense of anxiety, that familiar sense of hurt that starts deep in his chest and causes his fingers to shake. And Sam wonders. If he freaks out when Dean is in the bathroom, what's going to happen to him if Dean dies- no, no, no, Sam CAN'T think like that. Dean isn't going to die. Not as long as Sam lives.
One late night, Sam jerks awake from the throes of a nightmare. He's gasping, trying to draw in air like a dying man, and he looks around wildly for Dean. He can't see him. Dean isn't in his bed. The sheets are thrown back.
Where is he? Where is he? Where is he? This mantra runs through Sam's mind as he starts looking around the room, whispering Dean's name because he doesn't have the strength to speak any louder. Sam feels like he's drowning, like he can't breathe, like he's going to die in this very spot because Dean isn't here. Like a desperate man he flings open the door and looks outside, and he doesn't even notice that he's been tapping his knee incessantly over and over and over again.
Dean is there, sitting against the Impala, staring up at the night sky. The air whooshes out of Sam as the relief settles in, and he slides down the wall weakly, holding his face in his hands.
Resting against the wall, as Dean rests against the Impala, Sam knows that he has to get Dean out of this deal. If not for Dean, then for himself. Because if there's on thing Sam knows for sure it's the fact that his world will end if Dean dies.
Sam's sobbing, cradling Dean's lifeless head in his hand. It's over. Sam failed. He couldn't get Dean out his deal, and now because of him Dean is gone. There's blood on his hands, underneath his fingernails, it's on his skin, and it's in him. Dean's red, red, red blood all over him.
Sam's sobbing and he's trying to think, to function, but he can't. He grips Dean's hand, god it's so fucking cold. His other hand is going tap, tap, tap on his knee. 1, 2, 3. DeanDeanDean. 1, 2. 3. DeanDeanDean. 1, 2, 3. WakeupDeanWakeupDeanWakeupDean. 1, 2, 3. PleaseDeanPleaseDeanPleaseDean. 1, 2, 3. I need you.
The feeling is back in his chest, that same hurt that's been haunting him for months. It feels like someone's constricting his heart. Sam closes his eyes and waits, and waits, and waits, for the world to end, for everything to explode, so that he can fade away to dust and be with Dean.
Nothing happens. Sam opens his eyes and howls out his grief because he's still there.