Injuries or inflammation of any of these structures can cause shoulder pain, stiffness and diminished range of motion.
In your case, in the absence of an acute injury, overuse of your shoulder (especially repetitive overhead activities at your job or with exercise) and aging may result in inflammation of the rotator cuff (tendinits), bursa (bursitis), and gradual deterioration and eventually tearing of the rotator cuff.
Inflammation in any of these areas almost always cause night pain, especially if you sleep on the affected side. Chronically inflamed shoulders may develop scarring in the shoulder over time that eventually completely immobilize the shoulder joint, which is known as adhesive capsulitis or frozen shoulder.
Osteoarthritis, which is the wearing down of cartilage in the shoulder joint, is another common cause of shoulder pain, especially if you had an old injury that damaged your cartilage. Osteoarthritis may also cause night pain, weakness and limited range of motion.
A torn labrum may cause pain, locking or clicking, or the feeling that your shoulder will dislocate.
There are other diseases that can cause shoulder pain like a herniated cervical disc, but your history doesn’t really support this.
Depending on your history and physical examination, your doctor may want to do X-rays, an MRI, or an ultrasound for more specific diagnostic information.
Treatment options include applying ice or heat, non-narcotic pain medication, TENS (transcutaneous electronic nerve stimulator), physical therapy (including a home exercise program to continue stretching and strengthening and prevent recurrence).
I recommend activity modification by refraining from any aggravating repetitive activities, but you must maintain the range of motion in order to prevent stiffness. Gentle range of motion activities can almost never make your condition worse. .Ask your physical therapist or doctor how much you can use it and don’t immobilize the joint or wear a sling unless specifically told to do so. I hope this helps!
Andrew Pastor