We both have cheated but love each other

We met when we were 13 and we have been through many ups and down and the downs have subsided. H3 has done everything and the last time we have seen each other I caught him with another girl so I thought to retaliate I should kiss his best friend since he has done it to me many times. But now since I did that it's all about me and what I did. Not what he did. We have a child and we really cannot get enough of each other. Can we work through it or not? How do we do it? Anyone 3lse going through this problem?