Put your back up against a wall and drop a golf ball down your back, between you and the wall and locate it so it's on your shoulder blade. Put your right hand on your left hip and lean back against the wall pushing the ball in, work it around the area stopping on any knots and pressing harder, which should help to loosen the muscles around your scapula. Do this for your traps too and also up the erector spinae if necessary.
It's painful and will probably make you sweat a fair bit but it helps.