What Causes Pain From Shoulder Blade To Arm And Back?

I am having sharp pain in my shoulder. The pain runs form my shoulder down my arm and back, and also to my neck. It has hurt in the past form using in playing baseball or such activites. But recently the pain has been a lot worse than before and hasn't gone away for about 2 weeks. Ive taken medicine for it but it does not help that much. What do you think is wrong