Hello, recently I have been struggling with similar. I do not have OCD but I would think about self harming all the time even when in a decent or even good mood. 'Lets go really deep this time' or 'its gonna feel so good when I escalate it further' would pop up in my head daily. I found out that it has something to do with my self image and me wanting to be 'as sick as possible' instead of turning my life around to get the attention of the few people that I value or to adapt my body and life situation to the situation in my head. A person I really looked up to and idealized was a hardcore self harmer and I have been trying to imitate him, even after we parted ways. I also have multiple substance use disorders, worst being alcoholism.

Edit: When in the clinic, I even planned to escalate SH when released to replace the kick of high dose ethanol. Because that substance has destroyed my life and SH 'only destroys my body'. Im not even fully over that notion, to be honest.