Is it okey?

Need a bit of an opinion on something. Please dont be rude but all opinions are valued.

So me (27f) and boyfriend (28M) have been dating for few months and everything has been going really good. We both have gone through a lot and usually we both try to think from eachothers point of view. But since recently I have been having this nagging feeling about something from his past. Before me he has had fwb relationships and casually dated people. And I was the only relationship he had after 4 years of him casually dating and having fwb only relationships. Most of these girls has become good friends with him after they ended those relationships and two of them he considered as really good friends and still texts with them occasionally. Before I actually didnt care because those relationships didn’t involve any romantic feelings and they also had moved on and have relationships. And they know about me even though we haven’t met. One of those girls who lives in his hometown ( we are currently pursuing our post graduate studies so we live in another city) recently went through a breakup. My bf is going back to his hometown for summer and I cant join because I have other obligations. Today he said he is going to hangout with this girl during the summer and suddenly this nagging feeling came out of no where. I trust him and I know he only consider her as a really good friend. And even my rational mind says its so stupid to get this nagging feeling because I know him. But is it okey to have this feeling. She is his friend and its stupid to ask him not to hang out with her just because of my nagging feeling. If it was you will you be okey your partner hanging out with someone they previously dated even for like two weeks? Thanks.