What Causes Back, Shoulder And Neck Pain And Burning Feeling Near Chest?

Hello,

I have been experiencing a lot of upper back, shoulder, and neck pain for the past 6 months. During the past 4 days, however, I have had what started out feeling like a bruised sensation on my left side, right under my armpit to my breast. Now it has increased in intensity and I feel sharp pains, almost like an electrical shock.

Thank you for your help..