There is no one definitive answer to this question. Some factors that may increase the severity of endometriosis include: Having a family history of endometriosis. Having a high level of estrogen in the body. Having a history of pelvic pain. Having a history of endometriosis surgery. Having a history of infertility. Having a history of heavy periods. Having a history of pelvic inflammatory disease. Having a history of chronic pelvic pain.