Top left back and left hand arms pain and lower back

Hi Iam having pain in my left shoulder and the pain continues to my left hand arms as well. Iam basically a web designer and sit in front of a computer for long hours. I took a MRI scan and it show the gap between L4 and L5 is 1.5 (which should be 1.6 as normal) and the pain start in lower back and passes to top of left shoulder and continues till left arms. but sometime my lower pain is less, but my left back shoulder and left arms is paining continuously. Doctor advised for rest and back twist exercises which iam doing it. But still pain persists please advice. Pls reply