In my limited experience I've come to the conclusion that you can only trust a doctor to diagnose the most common diseases. Most GPs aren't even well versed in cancer incidence, and will dismiss cancer symptoms as something else, unless the evidence is overwhelming. But it's understandable that, when presented with a few symptoms, a doctor will be biased towards common affectations.

That leaves the burden of proof on yourself. If you feel that something is not right with your body, pester your doctor until you get a satisfactory solution. Unless you're a hypochondriac, that is.

Your doctor doesn't know everything just because they are a doctor.

You don't know everything just because you found something on the Internet.

Most patients seem to either doubt themselves or doubt their doctors but rarely, it seems, both. There's a delicate balance there.

But also, there are a lot of asshole doctors who will doubt you even after you've done your homework and have a compelling argument.

Source: Was one of the ~140 people who caught whooping cough in California in 2008. I figured it out, four doctors didn't believe me.

(Yes, I was vaccinated. Turns out the effectiveness of some of the newer combined vaccines (DTaP vs DTP?) dropped off more quickly, but they didn't update the booster schedules, leading to the most recent outbreak)

And a lot of well-meaning doctors that apparently don't take the time to do things right. Have a family member with RA that was almost given an injection for another condition that is contraindicated in people with RA, and it would have happened had we not done the research online and spoken up ourselves.

Multiple times we have found ourselves being more well-informed than the doctors, and it seems things are only caught if we bring them up...