What would cause severe lower back pain & work it's way up?

Commonly : Muscle spasms or sprain of the muscles and ligament of the back can do this. Note that other possibilities are possible, including those relating to the gastrointestinal, gynecological and urological systems and more information or an in-person examination is required.

Back pain: The back pain can be caused by muscle strain, spinal stenosis, ruptured disc, nerve impingement ... If the pain goes up, it might be a refer pain. If your pain persists, you should seek help from a health care provider. You might benefit from a comprehensive evaluation.