Lost

I lost my temper today. It wasn't just one thing it has been building for the past month or so. Kayla was asked to go to bed 45 minutes after we told her to go to bed the first time. So she went to her room, slammed her door, and started crying. I tried asking her what was wrong but She just kept saying that She was supposed to be in bed.   She has been having these tantrums ever since she got here over a month ago. I've tried talking to her but she won't talk to me. She hits me and disrespects me every chance she gets. Her tone and attitude need adjusting  but those are just symptoms. Yesterday she flipped off a random person in a car that lives in the trailer park here and when I came in to talk to her about it she was crying and not engaging at all. The day before she picked a fight with a boy that was younger than her and ended up with a sprained wrist, which She continues to use to injure herself. She won't talk she won't allow us to help her. I'm on the verge of cutting again or hurting myself in some other way. I don't know what to do. I don't know how much longer I will be able to hold out.