Although I'm only 14 I know exactly what you are going through.
I started cutting when I was 11 did it for 1 year and tried to quit. Instead of cutting I was expressing my feelings through drawing. You need a replacement. And just like everyone says, don't let one wrong step bring you off your path. Just step slowly step back and put both feet strong on the path again. I did that and haven't been harming for over 2 years now. You can do this, just get beck on the path.
I'm always here if you want to talk. You will make it. I'm sure. <3