Shoulder issues

I have been having some pain in my left shoulder for a couple of days and I can't seem to get rid of it.  I thought that I just slept on it wrong, but that doesn't seem to be the problem.  Its a constant dull ache in the back of my shoulder that seems to be radiating down my arm to my wrist.  It doesn't hurt to move it and I have had no problems swimming or biking.  Its just getting annoying.  I have had shoulder issues in the past from playing years and years of volleyball, but I never went to the doc.  This doesn't feel like the same kind of pain.  No popping or ripping, just an ache.  Anybody have any idea what is wrong with me?