This story has been driving me crazy and I've looked EVERYWHERE for it. So you guys are my last hope.

This is all I remember of the plot:

Dean somehow gets possessed but Sam can't tell and they go on living life as usual for a little while until the demon in Dean's body starts making advances toward Sam. I remember Sam being a little confused but when they finally have sex he gets all teary and is like "I've waited for so long for this". And then finally he figures out Dean's possessed, is horrified, fixes it, and then there's some angst but I think it ends happily. I think.

I know it's not much to go on, but does this sound familiar to anyone?