I don't even know where to start looking for this fic but I remember a few specifics if anyone can help me out.

Sam was a demon with huge wings and he is taken by angels (I think) and held in a small room in heaven. He can't stretch his wings out and it's hurting him, being in heaven for so long because he is a demon. I'm pretty sure it was Castiel, but someone is there with him watching over him, making sure he doesn't escape. I think Dean is a demon too and is the one who rescues him in the end.

Sound farmiliar?