Sandy it's werid that I would see this thread this morning and I don't know you or the circumstances totally with your X, but I have to say from my own experence with my X when I read these words I felt nauseous:
The other day when we were talking he apologized for all the a-hole things he did while he was with me. He said things would be different if we got back together. During our time apart he realized how much he loves me and how good I have been to him. And a whole bunch of other nice stuff that just made me feel even more guilty about cheating on him last year.
My X said the very same things and because I had longed for so many years to hear him say them, I let my emotions get in the way and we got back together. Four years I regret giving back to him. In hind sight I wish I would have given him ample time to prove to me that he really would be different, he didn't change at all which proves to me you can't change the spots on a leapord.
I am not the person he thinks I am. I think I owe him the truth so he can decide if he still thinks I am such a great person.
It's your life Sandy, you know him best and if he's not a manipulative person he might be sincere, and I can see why you would feel guilty about cheating on him. It's your call, one part of me says he deserves to know that you are the cheating kind before he decides to go back with you. The other part of me says, don't ask don't tell if you can live with the guilt.
I wish you the best whatever you decide.
Kate