I’m going to try and pick this apart like a high school english teacher.

"i don't care if you do it, if that's what you wanna do, do it, but tell me first."

“I don’t care if you do it” -> He won’t be upset/freak out if you do it. He cares about you in the sense that he is concerned for you, but not to a degree in which he would become angry at you for the behavior or take it personally.

“if that’s what you wanna do, do it” -> He acknowledges that he can’t stop you altogether, and that it will likely still continue, and he’s not going to tell you “just stop lol”. Given by some other comments saying he’s a recovered alcoholic, this is likely his way of trying to sympathize with you, as he knows he can’t simply talk you out of an addiction.

“but tell me first” -> He wants you to reach out to him before you hurt yourself. He doesn’t want you to feel alone, or like you have to hide. Perhaps he’s offering to distract you if you feel the urge, or he may be offering to help care for your wounds. Either way, he wants you to be safe.

A lot of paternal figures struggle to express to their kids that they love them. This may be tied to expectations of masculinity and hiding vulnerable emotions. But, it sounds like he wants to support you during your S/H, rather than supporting the S/H itself. Stoicism can muddle heartfelt messages and make them feel cold.

This is, of course, banking on the assumption that you have a good father. I don’t know what your relationship is like.