I recently stumbled upon a wonderful little fanfic that I completely forgot to bookmark! I'd like to read it again, but I have nothing to go off of except for what I remember. So here goes: It was early-season boys (season 2, I think, because it was shortly after John died).  They were on their way to their next hunt when Dean got a bad migraine. Sam had to step up and take care of him. I think I remember Sam being reminded of Jess because she used to get migraines too and so he knew how to take care of Dean. Is this ringing any bells for anyone else? I've searched high and low!

Found! It's Quarter Rest by pineapplefan92