Can't stop visualizing it in my head and am heading for relapse

Hey Fapstronauts, been reading for about a year now, first time submitter.

So I have been PMO free for a little over four months now, my longest streak in years. And my trend tends to be that after a while, what happens is I keep replaying porn in my head I have seen before in my head, over and over again, and after a while this whittles me down to a relapse. And this is happening to me again, and I have been having a really hard time just trying to not think about it, get my mind off it, and stay on this path. My gut feeling is "it's okay if you watch it every once in a while, once every month or so won't hurt". And I know not all of you are going for completely porn free (or at least I think you people exist here, sorry if I should know that), but for me I know that once I relapse and try to make it a one time thing, I think "Fuck it, X amount of times more won't hurt", and I will be going 2 weeks before I pick myself up again.

Any of you guys got any ideas?