Is it normal to be the one the cheater is with?

So this guy and I, we dated for so long. We were each other's first love and got super close. But recently something happened and we broke up. I ain't over him obviously, but he's a jerk so my friends tell me not to try and talk to him. I found out he got a girlfriend from a different city no one knows instant depressment. But like 2 weeks later...he texts me everyday being flirty and saying he wanted to see me, and how his girlfriend and him were constantly fighting and not working out. We talked from then on for like a week and a half straight So I visited him the othet day, he made a move and stuff happened. I find out after all this...his girlfriend and him are still together! I don't know what to feel except awful..is it normal to feel so terrible about this, when it wasn't my fault.