The truth about affairs, is that they often happen in MLC.
You can ask, but the chances of you getting a truthful answer, are slim to none. Even when confronted with evidence of an affair, MLCer's will try to lie or at the very least minimize it.
Worrying about it right now, puts your focus on him and his behaviors.
Focus should be on the only person you can control and that is you.
Read, learn, post. You are getting some good advice and great perspective.
"Acceptance doesn't mean resignation. It means understanding that something is what it is and there's got to be a way through it."--Michael J. Fox