What Causes Pain Between Breasts And Burning Sensation On Shoulder?

I ve been feeling cruddy since xmas. seems like a bunch of different symptoms. Started with lot of mucus coughing up. that s been gone for several weeks but also feeling dull pain that really doesn t hurt inbetween breasts as well as in burning sensation on back between shoulder blades. unexplained muscle weakness in shoulders and arms. an overall fatigue. a little sore throat that (i ve been diagnosed with salivary gland stones last year and thinking that s the reason for the sore throat ) but all these other symptoms are new. As the day goes on I get very tired. fatigue mostly. EXTREMELY FOGGY BRAINED. i feel like it s infection but not sure where.