I think I used to be kind of a hypochondriac back when I was depressed. I never really told people about my "suspicions," but I would read about various ailments and think "maybe that's what's wrong with me." It was also before I was diagnosed with depression, and depression was never something I had considered, or even knew a whole lot about. A lot of the "symptoms" I thought I had were exaggerated in my mind (and I think deep down I knew this, which is why I never made a big deal out of anything), but I did have headaches every day throughout my teenage years.
I'm not sure if this was a way of seeking attention, or simply because I knew there was something wrong with me, and I just wanted to be able to put a name to it, and know that I wasn't just "imagining" things. Maybe there was also a desire on my part to be able to explain/excuse some of my behaviors, like the fact that I missed a lot of days at school, or just didn't feel like doing much in general.
It was a relief when I was diagnosed with depression, and subsequently, social phobia, because then at least I knew that it was something legitimate, and not just me being lazy/apathetic/etc. But psychological disorders aren't always taken seriously, or as seriously as physical ones, so perhaps if you still feel convinced that there is something physically wrong with you, it's because it might "legitimize" your problems more (at least in the eyes of other people). I know in my case depression did cause the headaches (for the most part) and some other physical symptoms- when you internalize anxiety/stress your body will express it in one way or another.
So maybe you feel this way because you feel like those around you aren't taking you or your SA (or any other problems you might have) seriously. I don't know your situation, so my theory might be wrong in your case.