I think doctors aggravate this problem of people believing they're ill even when the clinical evidence doesn't support it. I can't tell you how many doctors I've had tell me, explicitly, within 15 minutes of having met me that they know my body, symptoms, and experience better than I do. It used to come much later in the process, after I'd spent months following their instructions to the letter and having my symptoms…
Just because you live in your body doesn't mean you know how it works. I drive a Civic, it doesn't make me a mechanic.
Diagnosis is tricky. Especially in a system as complicated and interconnected as the human body. People often have a bad tendency to misattribute effects to recent events.
And let's say your conjecture of why they dismiss you is true. That it's because everyone else is an idiot and they're not accustomed to dealing with the brilliance that is you. Everyone thinks like that. Everyone thinks they're the bright shining star who knows medicine better than the doctor. You were not the first person and you won't be the last who walks in with reams of printed out papers on the very thing they're sure is the problem.
They have no way of knowing if you actually know what you're talking about unless they put in the work of figuring out what's up with you. So yes, you could be right, but you could also be wrong. And the work is the same either way.