Why is my (previously mentioned) crummy ex-boyfriend messing with my feelings when he clearly does not care about me?

After a four months of being apart, no sex or anything, and a few revelations of more infidelity on his part during the relationship, I finally started not hating all men. I began to hang out with a considerate, compassionate, intelligent guy who sees nothing but my good qualities (for now anyhow). The ex is __flipping__! Calling, texting, trying to make me think this new guy is everything he himself is, while the whole time he’s still sleeping with two other women! What the hell??? I blocked him, threatened him with a restraining order, but he really hasn’t done anything to make me afraid. Just being obnoxious and unreasonable. Why would someone do that?