I cut myself i'm 14 and i need help?

im 14 i have a huge problem with cutting myself its usually on my left arm. I'm not sure how it started one day i was sad and really depressed and i just grabbed a razor and cut up my left arm. Its usually not very deep but enough to leave a scar and bleed for a little while. i'm scared because i don't know how to stop i don't know why i like it so much and i never know what to do after i cut myself. Like i know how to disinfect my razor and the wound i know how to clean it and bandage it i just don't know how to explain to people or my parents please help. i did it yesterday and i cut myself 53 times.