Hello wwwcitricacid: Thank's for sharing your struggles. I don't recall your having mentioned if you see a therapist. If not, perhaps doing so might help. I do think it's helpful just to have someone to talk to on a regular basis. Your family & friends can't do this for you, as I suspect you already realize.
I've had a bit of hypochondria over the years, although not to the extent it sounds like you are experiencing it. As I look back though, I would have to say that it was worse when I was young (around your age) & that as I got a bit older, (late twenties / thirties, etc.) it seems as though it dissipated. I don't know how common that is. Anyway, I wish you the best in your efforts to overcome these hurdles.