But are you saying to actually shove the gauze pad up inside there?
What I am saying is do whatever you need to do so that you are comfortable that this issue will not happen. But it seems to me that the gauze can be folded up to fit the contours of your rectum and then inserted. It would seemingly act as a better "dam", if you will, than cotton balls.
There are also butt plugs available as sex toys at sex shops. Never used them so just throwing it out there FWIW