Shoulder and right arm muscle pain.

I am having pain behind my right shoulder and pain in muscles of my right arm. It is worst in morning after waking up and sometimes pain increases if I turn my head to my right. It gets better if I take diclofenac 100 mg and also gets better if I raise my hand. Range of motion at shoulder joint is normal and grip strength is also normal. But the pain is bothering me a lot. I am not willing to take NSAIDS continually. I got an X ray of shoulder done on suggestion of my diabetologist and it was normal. He just told me to move my arm in all 3 planes 100 times in each plane everyday. Pain on the back of the shoulder improved but the muscle pain in the arm did not improve. I still feel horrible every morning when I wake up from bed or sit in office for prolonged time.                   My questions:- Can u suggest some medicine I can take at night for the pain in morning? Also is it safe to use NSAIDS daily along with zantac? Do I have cervical spondylosis or periarthritis of shoulder?