How to deal with depression?

I'm 16 years old, and lately I can't stop the overwhelming feelings of anxiety and depression. I feel anxious like I have to vomit, or hyperventilate at times. I hardly cry, I am a strong person. But recently, I find myself bawling about how crappy things are, or for even NO reason! I've had a really hard childhood. My mom is bipolar, my brother is addicted to alcohol and drugs. I lie with my dad currently, but am always moving. I've moved a total of 7 times this past year. I visit my hometown often, but family isn't really something I really have here. My grades suck. And I don't have very many reliable friends. Everything seems like it's a waste of time, or makes me mad. I just... Idk! I really hate when people act allemptional, but I've been freaking out lately and I don't know what to do... Help, please?