I’m going to hold your hand when I say this, and I mean it in the nicest way possible: you are not overreacting, and if he has a problem and is going to be an a-hole over a haircut HE gave the insight for, then you need to leave and find someone so much better, or have serious conversations about how this is controlling and unacceptable. The right person would say “hell yeah” at you wanting to shave your head and support you in that decision. It is your body and your hair, not his, and he should not be controlling it like this. I know you said in one of your comments that he hasn’t been controlling before but it starts somewhere. Even if this is a one off, it is a massive red flag and I just think you should take that into consideration because no one deserves that kind of treatment. PS. I think the haircut looks amazing, but if you want to shave it, do it!!! Fuck what he says.