idk what to do...

Posted about this a few days ago but. My boyfriend is still following random girls on instagram. As well as half naked models, girls he's not suppose to be having anything to do with because in the begging he cheated on me with me. And whatever. Well it's a big deal to me because it makes me feel like I'm not pretty enough, like these girls are better then me, and he rather be with them than me. And because he rarely had sex with me before I got pregnant, like 1-3 times a month, and now it's even less being pregnant.(but I know for a fact he wasn't getting it anywhere else) And I find it disrespectful. And because we've have fought over this situation 1000 times. And he keeps doing it. I realized he genuinely doesn't care about me or our relationship or he wouldn't do the one thing that hurts me the most. We haven't talked. And I haven't brought this up to him because he either isn't going to listen to me, or I feel why should I even say anything when I've been saying the same thing for 3 1/2 years. And yes it's my fault I put up with it and pretty much let it happen. Well it's different now because I'm 20 weeks pregnant. I just can't be with someone who hurts me over the same thing over years of being together. And I don't want my son to be raised to think this is okay. But it's so hard because I really do love my boyfriend with all my heart. And it's so hard to just up and leave belongs we live together and have our first child on the way. Just easier said to leave than done. I think I could afford my own place if I did leave if we can't work this out if we even should anymore, but I just feel so horrible having my son have split parents like I did because I never wanted that for my kids. I think visitation wouldn't be an issue I feel like we could work it out fine. But I'd also hate and feel like such a bitch if I got him for child supposed because I know how much he pays for everything now that he'd struggle and I don't want to do that to him, but idk if I could fully make it on my own. And it sounds bad I'm already talking about this and thinking about it. Because at the same time I want us to work. We were doing so perfect the best we have ever been then in one day he started doing this shit. And I'm just tired of feeling so unloved and so unwanted and tired of asking to be. I'm just so stuck and so hurt and I really don't have anyone to talk to..