I don't know what to do anymore. I've been cutting myself for 3 months now and can't stop.
That's not a healthy thing to do. Why do you keep cutting yourself?
I am depressed and it makes me feel better
You need to seek immediate medical attention both from a doctor and a psychiatrist. You need help with this situation because you should not be cutting yourself. You could do serious damage to your body.
I always heal up, but I don't want to stop.
This really isn't a habit to play around with. You never know when you could accidentally go too far. I advise you to get help from a doctor for this issue.