Hi, I'm the exact same way.. I give in to my self harm impulses a lot too. It's difficult to, and hard to hide if in obvoius places. I regret them a lot and the next day wish I hadn't but it goes away later on, for example; My story with self-injury is I end up getting so mad, hurt or sad and depressed that I take a razor or broken glass and just cut straight. I love the pain and it going away, but I hate that it ends up only lasting the night,
But I find listening to really upbeat, loud, rocking out kind of music helps. And if you don't like listening to music and just sitting there, you can take a radio player or iPhone and go for a run or to the gym. I usually love taking my anger out for a run and if not then maybe punching bags help caz I get to hit it a bunch of times.

hope you find other things, and hope this helps.
those are what I tend to do if I want to give in
im here if you ever want to message me to talk.
even if im just a stranger <3