Dean tells Sam about Ellen later than he probably should, and expects Sam to be angry with him, but he’s not. Instead, he nods a little and says “It’s not like Dad told us everything all the time anyway, right?”
He drops it after that, doesn’t mention that they need to go see Ellen soon anyway; he doesn’t mention Ash, because he doesn’t want to think about the things Sam might have him research, because all of them might lead to Sam being dead again, and Dean can’t handle that.
He wakes up in the middle of the night to Sam panting, sitting up straight in his own bed. The room is dark, but the light coming in through the shades from the parking lot makes the sweat on Sam’s skin stand out. Dean’s voice is sleep rough, but he says “Sam?” hoping to get a reaction of some kind. Sam just starts to tremble, and by the time Dean is pushing his blankets away to go to him, Sam’s untangling himself from his own bed and fumbling his way to the bathroom. When the door slams it makes Dean jump and the sound of Sam vomiting makes him wince.
It’s hours before it’s over; once Sam’s stomach is empty he just spends the rest of the time dry-heaving, and Dean sits on his bed listening and not able to do anything. He went in, once, to try and help. Sam looked up at him, eyes glassy and dark, and just said get out, his voice hoarse and unsteady.
The bathroom door is partway open, and he can see the pale skin of Sam’s arm and its quiet now, so he gets up, tries again. The bathroom door creaks and it sounds painfully loud; Sam’s lying on the floor, head pillowed on one arm, the other stretched out. “Sammy?” Dean tries again. He looks up at Dean and his face is drawn, pale; he looks too tired for this anymore. He’s too young to be so tired, and Dean knows it because he’s felt this. “Come on,” he says softly, “let’s get you up off the floor, okay?”
Sam just looks at him like he doesn’t see him, and he’s shivering. Dean kneels down, pushes damp hair back from Sam’s forehead. “You cold?” Dean asks him.
“I’m always cold,” Sam whispers, and it wasn’t the kind of cold Dean meant, but he knows how it feels anyway. So he gets a paper cup from the stack on the sink and fills it with tap water. He watches Sam struggle to sit up, and he knows how that feels, too; he knows how it feels to struggle to stand up, to stay awake, to make yourself live one more day you don’t think you should.
“Hey,” Dean says softly, kneeling down, holding the cup out to Sam. “Here.”
Sam takes it, hand trembling as he brings it to his lips. He takes a small sip, so small, and gags. He just shakes his head, holds the cup out for Dean to take it back. “I can’t.”
“Then just rinse your mouth; you’ll feel better.” Dean watches him swish the water around and spit it out in the toilet, gagging up nothing. “Sammy… What did-“
“Don’t,” Sam interrupts hoarsely. Dean catches his gaze and something in Sam’s face just hurts. “I don’t want to talk about it.”
“Sam, maybe – “
“Don’t ask me, Dean,” he says, turning his head away. “I’m not going to tell you,” and Dean knows him well enough after all this time to know the sound, the threat of tears in his voice. He knows Sam well enough that he has to let this go right now, because pushing it is just going to make things worse.