My bf and his stupid Facebook

Ive been with him 4 years. He knows a lot of females. I caught him like 1 and 2 years in talking/flirting/being inappropriate with them. He had long conversations and when he had Snapchat he’d send videos and pics of who knows what. He would like pictures of his cousins friends and they would literally have their asses out in their pics. You get the gist. So fast forward we’re talking marriage and moving out. We haven’t had an argument in a while. We haven’t see each other as often with our jobs. And This whole time he’s had his Facebook logged out and he won’t even open it or even have his phone open in general. I’m always saying he’s so secretive and he’s probably doing the same shit.

Well tonight we saw each other and had an argument. He didn’t text me or answer my calls for hours. He only responded with one word. I got fed up opened a fake Facebook and looked at his profile and it’s private. (I don’t have a Facebook for these reasons, because I don’t want to know what happens on his account) he posted a pic of us and I tapped it and saw who liked it and went to their profiles and all these random girls have hearts from my boyfriend on their pictures. And some pictures are them showing off their ass. I don’t even want to go looking for comments. I don’t know what to do. He won’t answer my calls, and if he texts me he says I’m being annoying and to leave him alone. I still haven’t told him. And I’m shaking and I’m going to see him in the morning. What do I do? What do I tell him? What if he waves it off and says it’s no big deal? He won’t ever open his account. I’m angry I’m disappointed.