Self harm is indeed a difficult addiction to break, I really feel for your ambivalent feelings, I am similarly ambivalent, it helps me so I don't want to stop, but I know it's not helpful long term. If you seriously want to try and stop, I suggest you try and find a specialist organisation with specialist therapists to help you identify what is driving the behaviour and how you can wean yourself off. It's never easy, but people swear that it's worth it.
I understand your need for a mark and for pain, it's not unusual.
I have tried to make a kind of peace with myself on the subject, self harm is understandable, if damaging, so punishing yourself or blaming yourself doesn't help you.
Be kind to yourself as best as you can, YOU DESERVE IT.