How do I deal as an adult with abuse that happened as a child?

when i was young my dad used to punish me by hitting me severly and throwing me into my room. I was deathly afraid of the dark when I was little and (my dad knowing this) would turn out all the lights so i couldn't see anything and close the door and told me if I turned the lights on he would come back in. This happened until I was 11 and the cops were called by my aunt. Further more, he knew he couldn't hit me anymore but decided screaming and yelling would work instead. So, to this day, I am still verbally abused by my father when he's drunk or when I talk back. I'm 17 and I now have extreme anxiety especially when I am in dark places or when someone raises their voice. I feel so alone and I'm scared to say anything to anyone. My mom knows about it but she doesn't think it's a big deal. How do I cope by myself?