Depressedgirl,
I must confess that my knowledge of what you are going through is very limited and I hope others can help more. What I will say is:

Firstly, you are not alone. You are not a failure. You are not a mistake.

Try to think positive. I don't know anything about your past or your traumas, but you say it's been a few weeks since you last cut. That is an achievement. Keep it up, minute by minute, hour by hour remind yourself that you're on a roll. That you don't need to cut yourself.

Again, I don't know anything about your history, but are there coping mechanisms you could use when feeling like this? When a friends daughter was young her parents split. The daughter started a habit of scratching herself or pulling her hair when she had been told off. The therapist suggested that she take that anger out on a cuddly toy or pillow.
Maybe you could find a field or open space where you can scream your lungs out when you feel this way? Maybe you could get yourself an old piece of furniture and go at it with a hammer? Anything you can find to transfer these feelings away from yourself and onto something that doesn't matter if it breaks.

I really hope that helps, even if it's just a little bit.