Right now I'm single but I really like this guy but the problem is that he has a girlfriend. What do I do?

I started falling for him at gradution and then we later started talking. I have never felt that I could ever be that open with anyone, but he made me feel so great and that I could tell him any thing. But I found out from someone else that his parents are makeing him and his girlfriend get married. So should I just forget about him or tell him how I feel.