OK so there are two dimensions at work here:

(1) having a variety of partners, and

(2) locking down the partner(s)' sexuality in that they won't sleep with anyone else.

Men want both of these contradictory elements to one extent of another, and they (potentially) stem from evolutionary drives:

Men want variety because of the drive to spread their seed, and they want to lock down a woman's sexuality so they can be more assured that the seed that sprouts into a baby is their baby.

Which are you? Would you feel differently in a more "traditional" society, or do you believe your preference is innate?