Hello, Thanks for posting on HCM, The reasons for lower abdominal pain associated to lower back pain are numerous amongst which you could have acute PID, UTI (cystitis or ureteritis or urethritis), colitis or abdominal colic or pelvic diseases such as endometriosis, PCOS, post-coital pain (could be due to cervicitis, cervical neoplasia etc. What you need to do to determine the cause and get it treated is - consult with a gynobs - who will probably request a series of laboratory tests and imagery studies - provide appropriate treatment depending on cause Hope this helps and wish you the best. Dr. Bernard