Hello and welcome to PC!

You have a decision to make about whether or not to stay with a liar and a cheater.

I truly believe people are cheaters or they are not cheaters. That's been my experience in my life. No matter what your fiancé says about his changing, I wouldn't count on that. He's a cheater and a liar. The lying is worse to me than the cheating, TBH.

I wouldn't think of it as 4 years wasted. I never thought that way. You had those years with him, he devastated you and turned out to be a creep, you got wise before you got married and saddled with his kids, and you got out and moved on to find someone else who truly loves and respects you.