Feeling Dismissed: How to Advocate for Yourself in Medical Settings

how do you deal with feeling like you're not being believed? It feels like no matyer what I do, my parents and doctors just aren't listening to me. I've been doing research on my symptoms. (not enough to diagnose, just enough to know what to ask about) but every time I ask I feel like I'm being dismissed. I get a lot of "that doesn't sound like what you're dealing with. Thats more like *insert symptoms I JUST described*" or (after me experiencing symptoms in front of them and telling them that thats what im talking about when I say I think I have ____) "idk, it seems like you're finding these things right after you it happens". Its also a lot of me saying "I think I have ____" and being dismissed then like 2 weeks later I talk about it again and get "Sounds like you have *thing I said earlier*. its very frustrating. I'm trying to not be too upset (especially with my parents) bc I know they're just trying to help and this is difficult for them too, but I'm starting to get agitated because it feels like we're going in circles and not getting anywhere. It could be a communication issue, but especially with my doctors I don't know how to be much clearer. Any advice?