A sacralized L6 (you probably mean a lumbarized L6) is rarely by itself a cause for lower back pain. There is a rare condition (Bertolotti’s syndrome) which can cause pain but again-unusual.
You need a work-up by a well experienced spine surgeon who can diagnose your pain generator and recommend a solid plan for potential surgery.
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.