This is my battle this past year. Okay, he cheated, he is bloody sorry, why am I not okay now? I have tossed it in the pan, sauteed it for a bit, then eventually stewed the crap out of this question for a long time. Chump Lady posted about it so succinctly, as she is want to do. Cheaters are not owed reconciliation just because they are sorry.
I’ll let her explain it better http://chumplady.com/2014/05/cheaters-youre-not-entitled-to-reconciliation/