Oct 21, - If you're feeling anxiety, stress, sadness, or irritation before sex, you may feel physical symptoms of nausea, pain, or gas after sex. Similarly, if. Aug 25, - When you're having sex, the muscles in the pelvic floor become active. contract and relax, the rectum is also connected to the pelvic region and sometimes contractions can cause you to fart. Nothing What happens to the gas after we fart?Why do I have back pain after sex?