Why do I have shoulder pain from swinging a bat and throwing a ball?

I'm 22 years old and starting playing baseball when I was 5, never had a problem. But a few years ago I reached far outside the plate to swing at a ball and hurt my shoulder pop with tremendous pain. I have since quit playing and still play softball once in a while. Every other swing it will hurt the same way, but sometimes I feel no pain at all. I'm left handed so when I throw a ball with my left arm it hurts a lot too. The heavier the ball the more the pain. So both of my shoulders are bad. Any ideas what it could be? I started doing some rotator cuff exercises thinking it was that but I am not quite sure. Any help would be appreciated. Thanks.