MdngtRain,
I have also struggled with intense impulses to mutilate myself "down below". The temptation is very strong ~ and I am a planner. Not a "last minute" kind of person. All of my razors have small wires every couple of mm, which kind of blows my plan every time. I'd have to do surgery on the razor, to make it more likely to cause a more serious injury.
Talking with my T about the temptations wasn't particularly helpful for me. He simply encouraged me to notice the dark thoughts & let them go. Kind of like watching a leaf travel down a creek bed. You see it, and you let it go. I'm unsure if he didn't understand the intensity of my idealization or what, I kind of regretted telling him about it though.
I never mentioned my desires to my bf at all though, so kudos to you for telling your gf! That's a big & brave step. Try to distract yourself whenever these temptations pop up in your head. Do something completely unrelated, to get your mind off yourself and your body. I can't think of any specific tips right now, unfortunately, but there are lots of distractions out there...look them up online!
http://self-injury.net/information-r...y/distractions
Very best wishes to you. take care!