changing password

So my boyfriend changed his Facebook password because he says I do things on his Facebook without him knowing like Addin people, updating his information his bio and everything else like if it was mine. I don't have one but i used his. So he changed his password and doesn't want to give me his new one bc of that, so i told him if he's hiding something from me and he said no should I belive him or am I wrong for overreacting? Was I wrong for using his fb like it's mine? Or should I be worried that he's hiding something I'm confused 🤷🏻‍♀️ 🤦🏻‍♀️😐