Cats butthole keeps puckering out?

I know its nasty... but I'm a worrier, so I'm worried. My kittys bootyhole has been randomly sticking out.. I can't find any info online, besides stuff about "prolapsed rectum" but I don't think thats whats going on because nothing is coming OUT of it, it just just "puckering" out, about a centimeter, now and then. It isn't out all of the time, she is acting totally normal, eating fine. Could it be an anal sac issue? I plan on getting her to the vet asap regardless, but I just had a new baby, so it may take a few days before I can get there. I'd love any info anyone has. Serious answers only please.. Thanks!