Parents VS depression


So, my mom and dad don't believe in mental illnesses. Even though my mom is an insomniac herself. Because of this, I haven't told my parents about how down I've been and how bad my social anxiety has gotten over the past two years (I'm also an insomniac). My cousin--Ethan--died from suicide last year (holy cow it feels like more than that) during the worst part of my lows, and that happened to be the week of my birthday as well. So, yeah, I've just been feeling really depressed, and I want to tell my parents but they probably won't do anything about it. Anyone have any ideas for what I should do? I'm just so stuck at the moment. (I'm 15 so it's not like I can up and leave or something)