I know exactly how you feel.
I don't believe in medication (because of my anxiety, of course), so I refuse to take panic or anxiety meds to help with this increasingly horrible afflictionm which I know is just circular. No amount of logic or reason can get me to stop analyzing every single ache, pain, and dizziness that I have as something terrible, and I like to think that - when it is unrelated to my hypochondria - I'm a pretty darn logical person.
Your story really hit me because it was about 14 and also with a brain tumor for me. I was absolutely convinced. Still am, in a way I guess. What's worse is that now I keep finding illnesses that I think I have that actually cause anxiety and general "uneasiness." Yeah, that just sets off a new attack.
I tend to be of the opinion that those life-questioning, self-realizing questions actually help with the anxiety. That everything truly exists, some how. I like thinking about things like the builder of the house I am sitting in, or a painter of the walls, and how no body will remember their names in the long run, but they still existed and here is physical proof of that fact.
I will never suggest medications because...well, you know. But I've been thinking about therapy to help me get my goals back in line and my life back into my own hands; you know, give less power to my fear and all that jazz. I haven't been in school or finding a job that I could love because I am too wrapped up in this panic, and I'm not even the only victim - my fiance has to deal with this crap on a daily basis and I know it stresses him out as much as it does me. Ugh!
Sorry for the rant...struck a chord I guess. I'm going to get help...hope this conviction sticks this time. :P