I use profanity frequently in sex scenes, for two reasons:
--My sex scenes are more often about lust than love.
--I’m a great devotee of dirty talk in sex scenes.
On the second point, though, my friend and beta Jomahawk recently gave me some sage advice: If one or both of the characters are capable of speaking full, uninterrupted sentences during sex, it suggests that they aren’t having that good a time. So now I try to be mindful of that.