https://www.scientificamerican.com/article/the-science-of-endometriosis/

Every woman with endometriosis has an origin story, a memory of the first time she knew the pain in her pelvis could not be normal. For Emma, it goes back to the day in 10th-grade history class when she blacked out. The sensation, she says, was how a pumpkin might feel when its insides are scraped. Her gynecologist assumed she was having bad period cramps and gave her birth-control pills. They helped but not enough. “He made me feel as if I were acting a little crazy,” says Emma, now in her late 30s, who asked to go by a pseudonym. “It struck me much later that when a woman's medical problem isn't clear-cut, she just isn't believed.” Not until about six years after the blackout did she find a doctor who recommended laparoscopic surgery of her abdomen to look for the cause of the pain. That is when she learned she had endometriosis, a disorder in which tissue normally found in the uterine lining, called the endometrium, escapes and takes root in other parts of the body. By then, the disease had carpeted her pelvic organs like kudzu.