I'm so lost and confused rn

I'm 35. I've had 4 serious relationships in my life, not counting my current one. All of them have been severely abusive in everyway. Fast forward to now and I'm in a relationship that I have been in for almost a year. He is absolutely perfect in every way. He treats me like a queen, he's loving and caring. He doesn't abuse me, he communicates and he's always here for me and he grounds my anxiety....most of the time. When we first got together we were an hour from each other and we went days without getting to see one another. He made the comment a month in, that he wasn't used to having to behave when he was hrny. I asked what he meant and he said he's used to having open relationships/poly. Nothing emotional wise, just sex. I was a little uncomfortable but he made me happy and I said well, I can't promise anything, but I can give it a try. I told him I wasn't going to do anything with others tho, bc that wasn't me. I just needed and wanted him. A week later he said he was done with that lifestyle, that he only wanted me and needed me. I was so happy. But, he kept changing his mind. Kept saying oh this is the last time I promise. But always went back to it. On three occasions when he said he was done, and without asking me if he could he went and slept with people. One time I knew he was hanging out with an ex and he knew I wasn't okay with them doing anything. But he did anyway. Most of the girls he does stuff with are his exes. I finally said this last time, that I didn't want to hear his promises anymore. Bc it hurts enough when he does stuff, but hurts even more when the promises are broken. I told him I don't want to change him. Do I wish it was just me? Of course. But, I'm willing to let him have this. I just don't know how to get my brain to understand that it's just sex. That he loves me and only wants that kinda stuff with me. But every time I know he's doing it and I'm at home waiting for him, I cry. I have anxiety I wonder why I'm not good enough. He constantly flirts and sends girls pictures and videos and sexts. Thoughts?