Self-administered pain

A few days ago, I did something sexual that I've never done before. I hurt myself on purpose while masturbating, to push me into an orgasm. To be precise, I pinched my nipples until it started hurting a bit. Not much, but enough for it to be more than just touching. That this actually worked for me was rather surprising, as touching anything but my pussy while masturbating has never done anything special for me. Touching my arm and touching my nipples was much the same thing, and I just figured that's the way it was. When other people do it, it's something very different. I can't tickle myself either, I thought it was much the same thing. Turns out, pleasure doesn't do anything but pain does. I'll need to experiment with this some more...