i can’t stop thinking about a boy

so i met this boy on a weekend trip and i CANT stop thinking about him, we talked all weekend and he is so patient, caring, and hilarious! We got along really well and i’m pretty sure he feels the same but honestly idk he could just be giving mixed signals... the only problem is he has a girlfriend but he failed to mention that the entire trip and when she called him he declined the call really quickly in a fashion that made me think he didn’t want to talk about it or he was trying to hide it... so either he is a bad boyfriend and he would actually cheat on her (which if you knew him you would think that’s very unrealistic) or he was just trying to not talk about it so we could get to know each other.... i’m not sure but we talk all the time and he’s really cute and quirky and i can’t stop thinking about him... and i know he has a girlfriend so i need to.... ADVICE NEEDED!!(