Yoga and losing weight is doing it for me but I've been told my back is structurally sound. Chiropractor said I have a frozen sacro-iliac joint in my pelvis. LMT said I have a chronically tight quadratus lumborum muscle on the same side. Physical therapist went farther and said my whole body was tight. Deep tissue massage was expensive and short lived relief. Core strengthening, stretching, and relaxation are all coming from yoga. And I've lost over 30 pounds since April.
Not sure if any of that helps you, but good luck.