Self harm relapse

I feel really ashamed recently because I used to cut myself for years. From the ages of 13-19 basically. I have scars all up and down my body and when I finally managed to stop I swore I wouldn’t do it again. I’m about to turn 25 and I’ve been having issues within my relationship and several nights ago I cut myself on my left side. I did again today. I worry that its going to become a constant in my life again as I have an addictive personality, I suffer from mental illness like BPD, bipolar 2, and extremely bad anxiety. I wish I hadn’t done it but at the same time I hate to admit it but it helps. Sometimes I just want to feel ANYTHING but my own emotions and its fucked up but the blade takes that away. Feeling the sting under my clothes helps. I want to stop though because I don’t want my boyfriend to find out. Any advice on coping mechanisms that have worked for you would be helpful. Thanks in advance to anyone that responds.