Let me begin by saying that this is not a "men are dogs" diatribe, nor is it an attack on women. If anything, I hope to illuminate what is often hidden in the minds and lives of couples. If this isn't going on in your relationship, then it is most definitely going on in the relationship of someone you know.

I should also say from the outset that men don't want to sleep with me because I am particularly good looking or sexy or interesting. I'm average in every way. The only thing that may be especially appealing about me is that I study sex and am comfortable talking about sex with men. I am interested in how they think, feel and act sexually. Even when I am personally uncomfortable with what they reveal, I am usually able to maintain a non-judgmental attitude.

When it comes to relationships, men admit that they want to have the best of both worlds. They enjoy the perks of a woman who works, mothers and maintains a household. They say, "I'm not an idiot. I've got it good, and I don't want to mess that up. I have no intentions of leaving my wife." However, they are often sexually frustrated and looking to supplement their unsatisfactory sex life at home with a fun and strings-free sex life on the side.

I asked one of these guys last week, "So are you telling me that as a woman, I'm either the 'good woman' at home making you dinner or the 'bad girl' that you're hooking up with after work? Are these my only two options? Be cheated on or be cheated with?"

"Pretty much," he said. "You just have to decide which one you want to be."

He is, by most accounts, a good man. I know him to be caring, intelligent and responsible. He speaks highly of his wife and said that whatever he has got going on on the side, his family always comes first. He doesn't dodge his son's basketball game for a quick hook-up. He says he is always up front with his side chicks that he will never leave his family. He said his last girl got feelings and broke up with her boyfriend to be with him (yep, she was cheating too), but he told her that he needed to stop seeing her. Once a side chick catches feelings, it's time for him to cut her loose. He can't risk her messing up his marriage.

Another guy I know has been telling me for months that his wife hasn't had sex with him in almost a year and he's about to explode and would I please be willing to have sex with him. In the same minute he's tweeting about the awesome church service he's at, he's texting me that he can't stop fantasizing about me giving him a blow job. The same day he's posting adorable family pictures on Facebook, he asks if he can send me a picture of him naked.

I could go on, but I think you get the point. If I wanted to be with a married man, I could have my pick. I don't. I have no intention of getting in that kind of mess. But some women are all too eager to be with a married man. Some women even prefer it.

I know it's possible to be monogamous. I did it for 16 years. So, possible? Yes. Probable? Seems not. Odds are, in any long-term commitment, someone is going to cheat. And even if they don't do it, they probably want to. Which begs the question, is monogamy realistic? If not, what is?

More on that in the next post...