What Is The Treatment For Throbbing Pain In The Shoulders?

I am a 34 yr old female with RA. This last week by back has developed a throbbing pain in my upper, below my shoulders blades, area. Some times the pain move lower to both my sides. My doc put me on meds for bacterial infection, but it does not seem to be helping the pain. ideas on what it may be? I thought maybe a kidney or bladder infection, as I have had them in the past, but now it does not feel the same.