After cheating on someone, is there really anyway to be faithful?Or is it a myth ppl can change?

You cheat on someone , because u were drinking and had mental problems .Now you are sober, on meds. Working out the issues that lead you to drink, do you tell the person you cheated?Or start over with them sober and working it out?You been married to them for 20 years and 6 of those years you were unfaithful and went on trips with your lover , who knew nothing about your husband.Besides being slime and stuff what do you do, given you have ended the fling with mister loverboy.