Good morning ma'am,  First understand the pain,  pain is just a symptom that indicates something not normal is the anatomical / physiological / biomechanical properties. Taking analgesic/muscle relaxants will spread the problems not the root cause. So,  better consult a physiotherapist, He/She will examine you and give you a better care. From your questions,  I assume it might be a some improper musculature in the back and sides of trunk . Sometimes it may be biomechanical back pain caused by hamstrings ( back thigh). It may be stiffened or weakened..