Honestly i think it is best to try and just stay in the moment when you are having sex, especially during the beginning stages of porn recovery. Gary wilson said on his website yourbrainon porn.com that the difference between porn fantasy and porn is “the mouse”. So even thiugh you used the qualifier of previous sexual encounters or future sex encounters it is difficult to tell where to draw the line and it gets blurred into porn fantasy pretty quick. I would say just avoid all types of fantasy to be on the safe side. Later on after the porn pathways weaken, maybe you can reintroduce this but for now, i wouldnt.Is it healthy to think about your previous sexual encounters? Ones with your spouse, not acting out.
What about fantasizing about future experiences with your spouse? Whats the difference? Are either of these "ok" since its with your spouse?