Your theory is an easy one to dismantle.
Monogamous species present with the genders equal sized. Polygamous species have the males twice the size of the female. A good portion of the species we are taught to believe are monogamous are actually NOT. They may only take one den partner, or are monogamous for one mating season but they have many other sex partners.
We are a promiscuous species, not monogamous or polygamous or polyandrous species and this is evidenced in one way by a smaller average size difference between the two common genders. If we were a or suppose to be a polygamous species YOU would have a tiny penis, internal testes and a much lower sperm count. Women would NEVER cheat. The only deviation from monogamy for them would be rape. Since we are a promiscuous species, you will find a wide variety of who fucks who and how and why.
Did you know that a woman can get pregnant by two different men and give birth to two different babies, one by each man? "Oats" is much better defined as "curiosities" or "desires" which everyone has no matter what their gender. Your reasoning and analogies are stale, already tried and already failed by many who came along before you in attempts to preserve sex as a male right and minimize the roles women wear in sexual pleasure and mating. It has also many times over, been used to argue why homosexuality is "unnatural". And in the same fashion as those misguided people before you, it is a self stroking and easy to justify your own behaviors tactic. Try reading some biology books, it can only help.