With the history given by you, I suggest you to consult a orthopedics doctor, since your x -ray and scan is normal as you told, you might have pain from the muscles surrounding the back bone, which generally happens if you worked excessively from past few weeks without rest or you might have sprain by lifting any heavy objects in past few days.if u r overweight, I recommend u take measures for ur weight reduction since it is one of the cause. For temporary basis use hot compression with a cloth twice daily and consult the orthopedician since the treatment for a bone related issue and a muscle related issue varies.