Moving on... Big sigh

I recently broke up with a guy I've liked/loved for three years now and we officially dated for a year and a half of that. We broke up because he cheated, for too long, too many times, because he didn't care enough to fix things. He now claims he's changed and he still loves me, I probably still love him whether I want to or not but there's this guy I've known for a while and he and I are sexually and emotionally involved, he's liked me for a while and I've just now realized it. I know he wants a relationship but my ex keeps lurking in my mind and my life... It's been two months but maybe about one since people really knew we were over. My new guy knows all the struggles with my ex, he's there for me as a friend and very nice sexually, we're practically in a relationship, just not calling it dating. I just want to move on so I don't fall back into things with my ex because it's too tempting. Is it too soon to officially be with my new guy? I know he really wants it...