Thanks everyone for contributing to this topic.
As you can see, many have had experience with this, and apparently, the main way you recognize it is when they change their habits/behaviors.
Which makes it even weirder... a person is bound to change in a relationship, so when they tell you, "I go to the new yoga class, three times a week, every morning from 8 to 9," you don't think they're doing it because they might be seeing someone during that time and cheating on you. In fact, you're encouraging them to do it.
It's as if nature pushes us to think about these things directly; we're programmed to do so.
But if you said your ex cheated, you somehow found out, and then you changed your attitude about the fact that when you hear a woman is cheating, what do you do now?
You don't think about getting proof, but rather, how do you behave now?
They are masters at manipulation; one used it as a pretext... she left WhatsApp open for her boyfriend to show how "honest" she was, but in reality she was using other apps to cheat (Telegram and Snapchat).
