Idk what to do...

I have been cutting for a while and I told a very trusted friend that if she doesn't tell anyone about it that I was going to talk to someone about it myself, and I wanted to to it myself. She didnt even listen to what I said and she told my school, and they called my mom. I know she was concerned but she should have given me a chance. its not really her buissness anyways. What do I do? Ny mom told me 2 hours before I had to go to bed that she know and that the school knows so now I have to go to school tomarrow and talk to people right after I found out people know. its over whelming and I'm panicking. I need to prepare for stuff like that and 2 hours is not enoght time. I need advice...