I think from reading numerous threads on this forum that many of us have a fair bit of medical knowledge from reading medical books and websites. I often find that, if I am watching a medical drama on the television, that I can diagnose "patients" pretty quickly. It always makes my husband laugh!
I was recently talking to a friend of mine who is a GP. She said that I reminded her of a 1st year medical student who had a lot of knowledge but no practice of seeing the symptoms in real life situations. She said that a lot of medical students have awful health anxieties to begin with. However, she said that once she started to practice, she realised just how much of her diagnoses relied on her experience about how ill people really looked.
My point is (although I find it hard to accept myself sometimes!!) is that we should try to trust in our doctors' oppinions as they do have a practical experience. I hope this helps a little