You are One Unit
Your back, your pelvis, your hips (and the rest of your body) is one unit of function.
Said differently, the muscles and other soft tissues of your low back are connected to the muscles and soft tissues of your pelvis, hips, legs.
You should get some guidance (from a PT and/or Physiatrist) how to do a general lumbo-pelvic stretching and strengthening.
And do it for the rest of your life.