What do you do if you feel like your life is falling apart?

I feel myself becoming a terrible person, I'm always irritable and angry and frustrated. And I swear I wasn't like this. I keep pushing everyone away, and although I'm aware, I can't help but do it anyway. I can't focus on my studies, I have no appetite, I think I'm just waiting for death to come find me. I don't have any motivation at all.