Why buy the cow when you get the milk for free? Keep spreading your legs for him....does it take a genius to figure out that's why he keeps coming back for more? Chances are his wife isn't giving it up or she's boooooring in bed, and he likes the action he gets in yours.
He feels guilty about his wife, then, he gets horny for something different again.
He'll never leave her.
He most definaetly is not committed to you.
Tell him to hit the road.
He is torn between two worlds the family and home world and than the fantasy world probably knowing what he is doing is wrong and feeling a very strong sense of guilt about what he is doing. He also has to divide himself thinking of his problems, his family's problems and yours.
He doesn't want to jeopardize his marriage (maybe he still loves her, maybe a divorce would be too expensive, maybe he's thinking of the kids....whatever) but enjoying his bit on the side too.