Welcome to the 2nd, uh, coming of the female sexdrive! I've recently been visited by this phenomena, too. I think about sex ALOT more now than I used to. Like, all day long.
Yes, I do this kind of fantasizing alot, too, and it does nothing to diminish my enjoyment with my current partner nor does it take away from the absolute pure delight
he brings to me. It's just the mind. Playing.