What should I do?

I'm in my 5th week of freshman year in high school and there is a guy I like who I barely talk to because I'm too shy. I had talked to him for the first time today by asking if we had any religion homework ( I go to a catholic school. And I already knew we didn't have hw, I just wanted an excuse to talk to him lol. ) when I saw him in the hall. He didn't pay much attention to me. He didn't even look at me or say "Yeah?" when I called his name . And the traffic was heavy in the hall and he couldn't really go anywhere so it's not like he was rushing or really didn't have time to talk to me. So I just asked the question. He just briefly looked at me, said no and that was it. Later in the day my friend who is friends with the guy I like said to me that he told her that he knows I like him cause someone told him. I told a few people that I liked him because I was trying to make new friends and wanted to find something interesting to talk about which I know now was a stupid idea since I barely knew these people and can't trust them. But now I'm trying to decide whether I should still talk to him and try to be friends or if it will just be awkward and to just leave him alone. (Also he has a girlfriend which makes it even more awkward and embarrassing but she goes to a different school. And don't worry, I'm not trying to get a guy who's already taken and be the side chick or whatever. I just wanted to be friends first and get closer to him.) So what should I do?