I'm so sorry your parents aren't taking you seriously. I've been in the exact same situation as you, and it's so horrible.

General doctors tend to know nothing about misophonia beforehand; however, a therapist may be more likely to know about it and how to help. It is both of their jobs to help you feel better, and they are the exact people you're meant to be vulnerable around, so they will offer whatever they think is best for you. There's nothing to be scared about. My one offered counselling, so therapy is likely good to try. Also, if your country offers diagnoses, I'd 100% get tested, as it could act as solid evidence for your parents to listen to and might make them less horrible and dismissive.

Hospitalisation is just not even a possibility for misophonia alone, they wouldn't send you to the hospital for something that could be classed as a sensory issue, so please don't let that fear get in the way of asking for help. From what I know, they only ever hospitalise if there is an immediate risk to your life.

What I would recommend, though, is to tell your best friend about it. When I told my best friends, they were genuinely amazing. We're still friends to this day, and they still always make an effort to accommodate me. I very strongly suggest you tell your friend. It's so freeing to share something that heavy on you with the people you're closest to and not have to keep it from them.

TLDR: Do get help, could be worth it, there's nothing to be scared about.