Idk what to do!!!

Hello everybody, so I met this boy at a Parade and he thought I was really cute and I thought he was cute and he seemed really nice as well. Later on since my sisters boyfriend knew him he had given him my number and we started texting. We met three times and we’ve known each other for about 3 weeks now but we are in different high schools so all the schoolwork and jobs don’t really let us see each other. Later on I came to find out he had a girlfriend the whole time he was talking to me... His best friend had told me and I’ve know his best friend for a while now and I knew he wouldn’t lie to me. And I’m just so frustrated because I don’t really know who to believe. The boy I was talking to keeps telling me that he doesn’t have a girlfriend and that he sincerely likes me and was only talking to me... I really just don’t know what to do because I was so hurt and mad when I found out! I just really need some advice on what to do.