His divorce may have nothing to do with you, but his behavior regarding his ex-wife does. If he didn’t want to get her sexts and emails, he would simply change his number. Or, barring that: If he wanted to make it clear to her that their relationship is over, I can think of nothing better than to continue to include you in all his correspondence with her.
If you were seeing me for therapy, I’d be asking you to think hard about the odds of someone like your boyfriend changing his ways. He has never been faithful before. I’m not sure he is being entirely honest with you now. There’s something about having multiple women vying for him that matters to him. It could be part of his bipolar disorder but that is treatable. It could be that his philandering behaviors are rooted in family patterns or past trauma or something else — in which case therapy could be helpful. But — of significance to me is that you don’t report that he is distressed about his history of philandering or that he wants it to stop. Quite the contrary. He seems quite proud of it.
The best predictor of someone’s behavior is what they have done in the past. Please continue this relationship with your eyes wide open and consider if you are willing to be conquest number 51.
I wish you well.