Causes of Pelvic pain. Pelvic pain has numerous causes, may be mild or severe and include: pelvic inflammatory disease, ovarian cysts/polycystic ovarian syndrome, endometriosis, adenomyosis, fibroids, ectopic pregnancy, appendicitis, bladder/kidney infection, irritable bowel syndrome and diverticulitis.1  Pelvic inflammatory disease (PID).elvic pain has numerous causes, may be mild or severe and include: pelvic inflammatory disease, ovarian cysts/polycystic ovarian syndrome, endometriosis, adenomyosis, fibroids, ectopic pregnancy, appendicitis, bladder/kidney infection, irritable bowel syndrome and diverticulitis. 1  Pelvic inflammatory disease (PID).