Sometimes, the answer to why we do something is simply - "Why not?"

In the absence of seeing something blatantly wrong, we figure - "Why not?" and we follow a course of behavior that seems innocent enough. Down the line, when we get the blow-back, such as you're getting, we come to learn a lesson. It is this: Just because something is not blatantly wrong does not make it a good idea to do. It is simply not a good idea for a married person to be reconnecting with an old ex. To say "hello" to someone like that when we run into them is simple basic courtesy. Anything beyond what basic politeness requires is asking for trouble.

This guy has no business messaging you on Facebook. That was brazen of him. Then again, you didn't discourage him. (You figured - "Why not?") Revisiting the past can seem harmless and even a bit fun. It is fun, but not harmless. It's a bad idea. It led to you flirting with him. I'm sure you didn't think of it as flirting, but it was. Flirting and getting flirted with is fun, no matter how old we are and no matter how many years we are in even the most terrific of marriages. It is just fun. (That is the answer to your husband's question.)

When Mr. Ex brought up the sex stuff, that was the clue that he was messaging you in order to flirt. Deep down inside, you felt flattered . . . and you flirted back. You weren't looking for anything to come of it, but it felt good. What married woman wouldn't be pleased to hear that some old flame still kind of has the hots for her? But it is simply a no-no. It sends the message to the ex that the door is not completely closed on the old relationship. It encourages the ex to come back for more.

This is a little bit off the subject, but I think it is a bad idea for anyone's husband or wife to be looking at one's Facebook messages. No one should be opening your Facebook messages, but you. That's going to be hard to fix at this stage of the game.

Another good rule would be: No talking to ex-beaus via Facebook. If you have those two rules in place, or at least one of them, then this will never happen again.