My bf is changing and he doesn't care...

So, to avoid any conflict between us, we have long only kept people who we are really close on our social networks... suddenly this girl appears on his fb, insta... and I obviously got thinking who the hell is that? apparently she is only a seminar girl they only say "bye and hi" altho we clearly before only kept real close ppl... i got a bit mad bcus he was "breaching" the rules... suddenly this little stupid thing turned into a big fight over many things that we didnt solve properly in the past, and honestly he doesn't even show to care... he says things like "if you leave im not onna die for you"... not to mention how "cold" he has been getting and distant.. the worse part is that no matter how much i talk to him and tell him "you need to change that" he just says he gives no fucks...