Can’t get over him?

I was talking to this one dude for 5-6 months. It was always up and down and I always anxious about the whole thing. We would hang out any chance we got and had so much fun together. We just clicked. A week after NYE things went bad. He started ghosting me and I wasn’t sure why. I found out through a mutual friend that he said I was being clingy. He gave examples of what I would do and some of them were lies. Others weren’t and I realized that I was a little clingy. I felt so bad and even thought of apologizing (never did). We haven’t talked in over a month and it’s definitely over. The same mutual friend said he recently started talking to this girl from his new job. I have also been talking to someone else since. Idk why but I just can’t move on from him. I feel so selfish talking to and hooking up with guys since and being upset hearing that he’s just talking to another girl. I think I just feel as if this whole thing was my fault and that if I wasn’t clingy things would be so different. I also just feel horrible for feeling like I wasn’t enough for him. Like I was for him to stick around for so long but just not good enough and that’s what I can’t get out of my mind. What do I do?? I need advice please!