Guy's Behavior

Why is he chasing me if he has a girlfriend?

I met this guy through one of my closest friends. He is the boyfriend of one of her other closest friends as well. He started calling me, texting me, and snapchatting me after we hungout for the first time (all four of us). He has straight up said that he likes me and that he has had a thing for me since last year, and he calls me almost every night and we talk for hours. He calls me baby, babe and cupcake. It bothers the hell out of me, and I have told him that... yet he continues to do it? He calls me beautiful, hot and sexy. He tells me that he loves talking to me and that there is something about me that he just really, really likes. He tells me that he can't understand the feeling that he gets when he talks to me, calls me or interacts with me. He keeps on telling me all of these things, and then he apologizes for putting all these thoughts in my head. Like what the hell? He says that he is going to break up with his girlfriend, but then social media says otherwise. He tells me that I better be single when they break up and always says things about 'us' being something. I want to be friends with him still, although I do have feelings for him. I just don't know what to do and why he is doing what he is doing. Why chase me and say those things to me if he has a girlfriend? If he was single then all of this would make me swoon and melt completely. But, he is not single and all of this stresses me out and really is taking it's toll on my mind and my heart.
Why is he chasing me if he has a girlfriend?
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