Im going to relapse, how do I approach it with my mom?

Im going to relapse soon, I just know it. I told my mom when I cut after the first few times. I told her I wouldn't do it again... welp I did. She was very upset. She still barely trusts me and that was about 128 days ago. I dont know what to do when I do end up relapsing, I dont know how to tell her. I dont want her to find out on her own like when I relapsed before but I also dont wanna tell her because she'll male me stop again and I just wanna cut without her trying to stop me. What do I do?