Go to a quiet place where the two of you can talk. Look directly into his eyes and ask him. If he is telling the truth-then he will look you directly into the eyes and tell you yes or no. Make sure that you examine your "evidence" before finding him "guilty" first. Good Luck.
many people are writing kinda cruel things I would say because it's not a mans nature for someone to like another woman you make yourself think you thus you start to do that, ask him straight forward when it's the right time too you don't wanna to seem anxious or anything. good luck!
Ask him in a casual conversation when you're gossiping about other people, say: *So, like, what do you, like, think about, like, Jennifer? Isn't she like, soooo fake? Like OMG!* If he defends her, he likes her.