Undiagnosed Bipolar, but researched and positive I have. And the struggle with parents who believe I'm ok.

Since I was small I've had small outbursts of emotion. Recently this has gotten worse with bad reactions to pressure, different opinions, and infractions with my dad that shouldn't be. I also make really bad decisions and my mania happens when my dad is mad about my outbursts of emotion. I'm usually hyper and really happy with friends and depressed after big fights or the loss of a friend. Plus when I start homework Im really excited and then I just drop it in the middle. Same with creative projects and relationships. It's been a big struggle and I haven't had help with my Bipolar Disorder, I was wondering- how can I help myself or receive help? Because my dad won't believe me and my mom won't either because they'll believe I'm faking