it's generally seen in relation to childhood sexual assault. if that may be something that you think fits, there is soemthing I found recently here. that's the first place I have seen the stuff my trauma T's have said in writing. generally, it is written about in relation to psychosis.
If not, it may be a bdsm thing? Or maybe somewhere along the way you started associating the release of cutting either as strong as, or with the release from an orgasm. it's something to explore with a T if you have one. You can also post here or in the sexuality issues section (can't remember the forum name exactly, but it's a bit farther down the page). There are a few people here who could relate (myself included)...