!
I know you don't want to hear it but your mom knowing is the best thing that could've happened. I've been a "cutter" as they call it these days for years, I first started it during my Freshman year of High School, I am now a freshman in college. I sought help for it once years ago when MY mom found out. And I did well for a while but it didn't last too long, my mom still has an idea I do it, I am sure...but she doesn't always say something, instead she just fears and cries for her daughter. It is so tough on our parents and we don't see that. I know I've seen it through everything we've been through dealing with this, but I still can't stop from doing it. It's after I've done it I think about my mom and how she'd feel.
It's tough, but it is good she knows now. You really don't want to go down the cutting path, I hate it, it becomes an addiction and I HATE it so much. Best of luck to you, if you need to talk feel free to PM me!