Boyfriend Has girl “best friend”

He says he liked her in the past, so I really don’t trust it. The thing is, I use to not want it to be true that he could still potentially have feelings for her but now I sort of do want it to be because I’m just tired of seeing it and second guessing us.
He’s a sweet guy, I don’t think he’s cheating on me right now but I fear what may happen in the future between them and I just don’t wanna be involved. Can I please have some opinions