Judging from your other posts Squish it sounds as if you're a woman in her twenties or thirties, a bit early to be losing control. Have you had similar accidents or leakage under other circumstances. If you have, you likely need medical intervention. But, if this is an isolated case then let me make a few suggestions.
* Just to play it safe it may be advisable to try and have a bowel movement just before sex.
* If you are in the middle of intercourse and you sense some looseness there is nothing wrong with excusing yourself and trying to have a bowel movement. If you have no immediate results on the toilet then it could just be a sensation intercourse creates for you.
*Not much separates the walls of your vagina from the walls of your colon so even though you may not feel the urge to have a bowel movement prior to intercourse it is entirely possible that when your partner penetrates you vaginally that the pressure from his thrusts pushes out some of the fecal matter that normally would have come out later.
Finally, if this is a reoccuring problem, allow him to give you a mild, low volume enema as part of foreplay. Fleet Enemas are convenient and premixed and it may be all that you may need. Make a quick visit to the toilet to expell the enama and simultaneously elimat the possibility of another mishap. You'll feel better physically and allow you to concentrate on the pleasures of the moment instead of fear of embarrassment.
Good luck.
ED