When you say the pain started “deep in the left hip”, the “hip” location is commonly misconstrued as to actual location. Was it pain in the deep buttocks-signified by where the back pocket would be on a pair of jeans? Was it pain right off midline at the “belt line” where a belt would hit the pelvis? Was it pain on the side of the hip as where a “six gun” would lie if you were wearing a holster or was it pain in the front of the groin as where you would put your hand in the front pocket of your jeans?
I will assume that the left arm symptoms were a reg herring and not related as these two areas are generally not connected.
A pain that is a “tight band around the rib cage” certainly sounds like it could be a thoracic disc herniation. The evolution of your pain could also fit that disorder. A thorough physical examination could go a long ways to determine if this is a cervical, thoracic or lumbar disorder but my money is currently on the thoracic spine. If you are given only one chance to have an MRI, make it a thoracic MRI.
Difficulty with defecation could be related to the narcotic pain killers you are taking as these medications slow down the gut.
Dr. Corenman
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.