Sure, advocate for your own health. (Though if you're constantly having to "advocate" because the evil mean doctors just won't take you seriously... well, the doctors aren't the problem.) But "I think I have this" isn't advocacy. It's arrogance. Your PhD in Google Medicine does not put you on the same level as an actual doctor, FFS.
Medicine isn't a fucking restaurant; you can't pick your diagnosis off a menu. You can, and should, explain your genuine, life-disrupting symptoms, and request that they be taken seriously. That's advocacy, and is it sometimes necessary? Sure. Some doctors are incompetent. But you know what they say about assholes: If you run into an asshole in the morning, you've run into an asshole. If you run into assholes all day... maybe you're the asshole.