My 14 year old son keeps getting detentions and he doesn't know why

Firstly, please forgive me if I don't use the right terminology but I am trying.  My 14 year old son is not clinically diagnosed but I am in a conversation with the school about it.  He doesn't want a formal label and I can understand that.  Anyway, he seems to go through phases where he gets a lot of detentions and he says he does not know why.  During this phase, he will often be very moody.  He gets into a cycle where if a teacher issues a detention, he is convinced the teacher "hates" him, and he then disengages from the lesson and is more likely to get a detention again.  It's never for anything really serious - usually not following instructions, not listening, being repeatedly disruptive through talking.  I have explained to the school that although I know they have rules, he tends to go on a downward spiral once the detentions start. He is a clever lad and after a few months in high school he began to make some nice friends, but I think sometimes they disengage with him because they sometimes see him as a bit naughty.  He has an OCD issue that is really impacting on his daily life and he regularly tells me and others, including his friends, that I don't love him or care about him.  This often stems from me saying no to him about something or trying to get him to do his homework or just generally stuff that he doesn't want to do.  I think there is an element of PDA and I try to phrase and approach things differently so he isn't overwhelmed by requests but everyday life is full of them. Does anyone have any advice for the best approach to trying to tackle the behaviour that leads to detentions and to support him through what might be anxiety?  I am not sure what I am asking really.  It's just that at the moment everything is a bit fraught.