I had a shoulder injury a few years ago, fell in the snow and jarred my shoulder trying to catch the fall, turns out the shoulder is a complicated joint. I got fixed with a combination of cortisone shots and physio, it took a year to get back to normal and it hurt like crazy - swatting a fly with a towel had me almost in tears with the pain. Luckily the MRI showed my rotator cuff wasn't torn.
I'd get it checked out asap and get the MRI done first in order to find out what the real issue is.
Good luck Danny.
Phil