Complex Joint. The shoulder is a complex joint, & many conditions/ injuries (rotator cuff injury, bursitits, tendonitis, labral pathology, etc).Can cause pain/ weakness. Some injuries of the soulder occur due to acute injury and some are from overuse. Ii suggest you see an orthopedist for a exam b/c many times "night pain" can imdicate an issue w/ the totator cuff. http://drmarkgalland.com/category/shoulder/.
Pinched nerve. A pinched nerve can cause neck pain headaches, and pain or numbness running into the arm. There are other potential causes, however, and so it would be good to just get a regular check up to make sure it is nothing else. An MRI can confirm the diagnosis. Therapy, chiropractic, and interventional pain management are the non operative treatments for it if it doesn't get better. Thank you.