Should I tell my new partner about my sh?

About a week ago we made the relationship official after a few months or seeing eachother and going on dates. I have been using self harm as a coping mechanism for the last 6 years, and at this point I don't think I can stop. I've told my partner that I've self harmed in the past, but made it sound like it was something fleeting in high-school. They don't know its an ongoing thing. When or if would it be a good time to them, or just wait and see if they figure it out? I feel like ought to be honest now, so that they can leave if it upsets them. But at the same time its such a trivial thing, and it feels like I'd be making a big deal out of nothing when I know that they are dealing with worse shit.