I woke up with really horrible pain in my shoulder in the middle of the night. the pain was right at the top of my shoulder & it went up the back of my neck to the back of my head. tylenol & heat helped but its still hurting what could cause this?

This requires a thorough examination, as the pain generator could involve shoulder joint, brachial plexus, or neck. Persistence of the pain, if associated with numbness and weakness in the ipsilateral arm might represent thoracic outlet syndrome or Parsonage-Turner Syndrome. These are possibilities which your doctor should be able to sort out.