Suspicious boyfriend??

So my boyfriend is always acting suspicious about his phone, he doesn't use it around me, he doesn't charge it when we are together (just lets it go flat), he goes for my phone instead of his. I feel like he's hiding something from me but I trust him and I hope he isn't. He also changed his Facebook password, I know it sounds stupid like yeah it's his own privacy but he expects to know mine so he gave me his and he changed his and hasn't told me. I change mine and told him and then he didn't even mention it. What should I do? I don't wanna be like "why didn't you tell me you changed your password?" But I feel like he's trying to hide something from me