If you're a woman, shoulder pain can mean ovarian issues - it defers there.
I apparently have frozen shoulder - I've been having a lot of trouble reaching up with my right arm, and finally asked my massage therapist to work on it. After kind of taking my shoulder apart and putting it back together - it's different now, and I'll see in a few days if it's better. I'm right-handed and mouse a lot. Took 2 big glasses of wine to anesthetize the pain of the therapy, too!