Since I'm not a cutter, I know I can't really identify with what you're going through, so excuse me if this is totally stupid or unsympathetic or completely irrelevant.
I don't cut myself, but I like to pick scabs. If there aren't any scabs, I am tempted to make some... but of course that would involve cutting and then waiting a few days. So instead I smear Elmer's white glue on my hands, and let it dry, and then peel it off. I've done this for as long as I can remember. It's not self-destructive, it's cheap, and the only problems occur if the phone rings while I'm still "gluey."
Might be worth a try. Meanwhile, I wish you well. As Jonsi said, don't give up.