Also, your "symptoms" can all be stress related. When I had stress issues and anxiety issues I would have loose stools, felt weak with no appetite, I would feel so tired and yet I couldn't fall asleep at time.
I even would have clumps of hair come off my head due to the amount of stress I put myself under.
I have to say I agree with the doctor, you have little to no risk. If you cannot feel reassured by an expert, then perhaps the only thing that will calm you is taking an actual test.
Personally, I think the stress and anxiety is causing you to over-analyze every little itch, pain, bump, bruise and you are driving yourself crazy. Stress and anxiety does some messed up stuff to your body. When I was stressing myself out, I would have little bumps form up and down my arms.
People get past it by being reassured by a professional, talking to your primary care-provider, being tested and sometimes seeing a professional to discuss these issues of anxiety.
If you think you cannot get past thing, perhaps you should speak to a professional about your anxieties.