The longer I hold off the worse I feel

Hi guys. Ive been struggling with self harm since I was about 11, and I'm 25 now. It's been quite a long battle. Right now I am 6 months clean. The longest I have gone is almost two years. But I always seem to come back to it eventually. It has always been a coping mechanism, an outlet for all the negative emotions. And also a form of self punishment for all my failings, penance if you will. It helps to relieve the anxiety induced self loathing thoughts I feel. Anyways, I have been trying really hard to stop because I know it is not a healthy coping mechanism, and I know that it negatively impacts my friends and family. Especially my boyfriend. He feels guilty over it because he feels like he should be able to prevent it. So despite near overwhelming urges I have held back and not done it. But the longer I go without cutting the worse the urges get. With each passing day I step away from the knife, the voice telling me to pick it up gets louder and louder. It's like a pressure. If I don't let off steam it builds and builds. I'm scared if I don't let it off soon it will explode in a big way. If I just let out a little, maybe I can hold off the big explosion. Would that be so bad?