hahaha i so do this! this past year alone i thought i had diabetes, TMJ, tumours, heart murmurs, heart problems, lung cancer... the list goes on.
the only legitimate thing that was wrong with me was that my old house had black mold. i had terrible headaches for months (this is why i thought i had TMJ or brain tumours) and the doctor kept telling me i was fine. i found the mold in a crawl space (lots of it! :S) and we moved immediately. i asked my doctor if that was what was causing my pain and he said more than likely. we moved and i have not since had headaches like those. thank god!
the power of suggestion sucks. i know how hard it can be to trust doctors, you feel as though they are not taking you seriously, you feel as though they are not testing enough, etc... i have recently been able to overcome my hypochondria (i think, i hope) and i hope you can too.