My best friend who is also good friends with my Boyfriend said that my boyfriend said that he "did things with another girl"(like while dating me) which this girl is the same girl my ex cheated on me with at his own party. Ive talked to my boyfriend and he said he'll completely stop hanging out with the girl even though he says they're "friends" and nothing else. I want to believe him but should I? Like I've talked with him about it but not 100% sure he's telling the truth.