Seeing a guy for three weeks, found out he has a girlfriend

So, I met this guy about a month ago, at first we talked he was always very nice and then one day he asked me out and I said yes. He went through a lot of trouble finding good places to go that I would like and we had a great time, kissed and nothing else (we haven't done anything else). He kept in touch, saw him again where he works and he kissed me before I left (in front of everyone). Then again we went out together with his brother and best friend, had a great time kissed again he called me two days later invited me out with his friends and I really hit it off with his best friend's girl, then somehow the girlfriend thing came up and I asked her, I told her I wouldn't say anything that I just wanted to to know, she told me he does have a girlfriend but that she is never around, never comes out and that she barely knows the girl. Now, I started to really like this guy, how do I confront him (remember he can't know his friend told me), I don't want to break a relationship but it also seems like he likes me, I mean he hasn't even tried to sleep with me and he always texts me saying that he has a great time with me. he knows he's not gonna get any for while, and I find it weird that the girl is never ever around to the point that he would take me out and kiss me in front of people and call me at random times. Is he maybe unhappy? I have been in that situation where I'm through with someone but can't let go, is that it? PLEASE SOME ADVICE!
Seeing a guy for three weeks, found out he has a girlfriend
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