My ex dumped me bec I fooled around.

My ex dumped me bec I fooled around. I was devastated, but found a way to get back on track, now that I found a wonderful person and I'm very happy (getting marrried soon). So NOW, EX becomes bitter and irrational bec. IM HAPPY, and he's not. Before,my ex sort of gets satisfation that I was running after him. Now that I'm not, it pisses him off that he's still wallowing in shit and I'm not. he refuses to give back the neclace I entrusted just to vex me. What a loser.