Looking back I think the biggest indicator was inconsistency with moods My wife's moods would often did not match our home environment while she was having an affair. On some days I could do no right, on other days I could do no wrong. When I repeated rights, they became wrong.
For example, I took our boys camping. She loved it, I thought. She called me often. I thought maybe she was thinking I was being a great father and that she missed us. However, she was not so nice the next time I took our boys camping. It was her guilt driving her mood, not our comping.