Sometimes it’s hard to remember how it actually began, but now there are certain movements that cause pain, like combing your hair or scratching your back.
There are up to twenty muscles involved in operating the shoulder and all of them are vulnerable to strain. When a shoulder muscle becomes weakened and dysfunctional through injury, associated muscles have to take up the slack. Eventually every muscle in the region has joined the party.
Massage can be very effective in treating and freeing up the shoulder joint.
I would recommend committing to four half hour sessions to make a difference to your shoulder.