I'm single and don't have to make excuses to anyone but if I were punting with any regularity while being in a relationship I'd try taking up a hobby that you can engage at will.
Sports seem to be the easiest choice here. Gym, basketball, tennis, martial arts, snooker, table tennis.
Anything that you might enjoy but don't have to commit full on. That's what I would try. No idea how far woman's curiosity can make these go to shit.