I don't know what to do :(

So I've been seeing this guy recently and we just get each other, like i've never connected with anyone so much and he feels like same. It's been around 5 or so months and we're both hoping on getting a relationship. We literally spend all of our free time together and he gives me all his attention and all that fun stuff. He's been literally a dream like I dont think i could ask for anything more.
However.......
He told me that hes been messaging a girl and she's been asking him oral and whatever, and told me it was all a joke and he'd never actually do it.
So i asked to see the messages but he never showed me in full.
I know it was more than that because my friends told me the day he told me, how there was more to it, about how hes planning on meeting her and having sex with her and anal and whatever.
He told me it was all a joke and it didn't mean anything, part of me wants to believe him because i dont want to lose him. When he told me about it he was all crying and telling he doesn't want to lose me.
I honestly like this guy so much and i dont even know what to do and what to think of the situation.