Wondering What Your Opinions Are

So my ex and I had been together for 2 years, but we were friends for 10+ years and I was MADLY, INSANELY, UNCONDITIONALLY IN LOVE with him.... When he broke up with me it absolutely crushed me, and I later found out that he cheated on me with multiple women .... It's been 7 months since the day he broke up with me (and since we've talked) and I truly feel like I've moved on from him, but lately, I find myself thinking about him and dreaming of him .... I don't want to, and I don't even know why this is happening because he really hurt me.... Anybody know why this is happening and how I can stop it?