can't let go

I need some advice. Me and my boyfriend have been together 3 years. Last October we broke up for about 2 weeks, over us fighting so much. During those 2 weeks he texted 2 of his ex's. One of the ex's was a serious relationship he had for 4 years. I never saw the conversation between them and it's absolutely killing me lately thinking about the "What if they talked about this" thing. He's talked to her a lot throughout our relationship, in a friendly manner but he knew how much it bothered me, and he still kept talking to her. Well after about a year and a half I told him to leave her alone or I couldn't be with him anymore, and he finally stopped until we broke up. Anyway moral of the story is he talked to her when we broke up and I have no idea what their convo was and it's realllllly bugging me. I know he talked to her cause I asked him if he did and he said yes, and I asked him what the conversation was and all he said was "I asked her why we broke up" and I was like why in the hell did you ask her that while you and I were freshly broken up?? And all he said to that was Idk closure I guess. THEY BROKE UP 3 YEARS BEFORE WE GOT TOGETHER. It's really starting to make me wonder if he was telling her he still had feelings for her or something.. ugh someone help 😭 yes we are together now. we got back together after being broken up for 2 weeks in October.