Jun 24, - As a result, you may experience pain and bloating. "Signs of a retroverted uterus are pain during sex and painful menstruation, but often it has no symptoms," said Dr. Wider. If you're having unprotected sex with a man, his semen can cause stomach pain and cramping after sex. 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?