I can't give advice here because I stayed with a cheating spouse for 30 years. There were many physical affairs, the last one I know about was 10 years ago. Her husband called me in the middle of the night and said that his wife was in a motel room with my husband, etc. etc. All I can say is that "once a cheater, always a cheater" - much like a child molester. They can't give up the thrill. They will always show the sames signs of cheating, however, so be on the lookout for them. And don't think that when they get older they outgrow it. . . they don't. Then, at 50, you realize that you've wasted your whole life on a worthless piece of s***. If the anger doesn't kill you the humiliation will.
but, some of us learn the hard way!