Search Results: my girlfriend likes another guy and left me

So evrrybody likes him and think he's a cool guy. He's had a good number of girlfriends. I haven't dated or kissed any of the guys or even showed interest. he knows everyone so he probably knows. So he used to be very flirty-he'd state into my eyes from across the room, check me out a lot, try to make me jealous, be chilvarous... We finally did have a long conversation at a mutual friends house and he complimented my personality a lot and seemed to hate my guy friend. He kept talking to me and standing close to me for no reason. And I was too shy to show interest. This went on for 2+ years. I only saw him once a week if I was lucky. So now he ignores me. He doesn't state at me openly like he used to. He acts like I don't exist, he doesn't even say hi. (He never did but he always was flirty) But every time I see him he stands close to me. One time he was with his buddies on the other side of the room and I was by myself. He came over behind me and I could feel him staring. I left. I got the courage to follow him on Instagram and he followed me back 1hour later. I liked his pics but he didn't like any of mine. Another time he left his friends again and stood behind me (I was by myself) and I could feel him staring. Today he ignored me completely. Sure we're in completely different friend groups and I came to class early and left late but he could have reached out. What's going on?