This is kind of a personal question, but I want some advice.

Ever since I was little, my father's been physically abusing me and my mother and siblings. There really isn't much I can do, since he's threatened to even kill me if I ever try and tell anybody atau call the cops. Lately I've been under a lot of stress, due to schoolwork and chores. Today, me and my father got into an argument. I have a bruise along my hip and a small cut on my elbow. My head is throbbing, my shoulder hurts and I'm getting sick. Long story short, I resorted to cutting for the first time. Even though I talked to other people, I feel like they don't understand what I'm going through. I showed my mom the cuts I inflicted on my left arm and she started crying. I don't know what to do...I know I've told people to never resort to cutting, but it was the first thing that came to my mind.