I'm amazed by the people -- I typically think women -- who expect their partners to never notice other women and never have a fantasy about other women and never fantasize about the woman in question doing anything more erotic than baking bread.
If she thinks he's imagining her sitting in church every time he takes her, she's seriously delusional.
Truth: He's fantasizing about others. He's fantasizing about unspeakable (to you) acts. He's fantasizing about you doing things you've never imagined.
And if you think his brain is consumed by wholesome family thoughts at the moment he's inseminating you, then your fantasy life is richer than his.