As per ur history. .it's most probably a back spasm...take muscle relaxants nd  hot fomentation.....if still persists get x-ray done nd consult pain specialist for evaluation nd treatment.

Hello, Low back pain is caused by injury to a muscle (strain) or ligament (sprain). Common causes include improper lifting, poor posture, lack of regular exercise, fracture, ruptured disk, or arthritis.Often, the only symptom is pain in the lower back.Most low back pain goes away on its own in two to four weeks. Physical therapy and pain relievers can help., for muscle strain and sprain. Avoid lifting heavy weight, sit, stand and walk straight, you can do back stretching exercise to prevent backache, Consult orthopedician.