It started right after I had my son-9 months ago. A constant, underlying, deep, dull pain under my right shoulder blade. You will notice me moving my arm around all day to try to massage it. It's not a bad pain at all, and hardly noticeable. It's just dull and there. I don't know if it's muscle strain from me carrying my son around all day or if it's something more serious. Have you ever had this after having your child?