I had this - a physiotherapist acquaintance got me on her table after I described symptoms similar to yours, and deduced that the problem was between my shoulder blades - many years of poor posture had left me (quite literally) lopsided - took about 40 minutes of fairly intensive (and painful) pushing and pulling of my back, rib cage and other various bits to get me somewhere near straight again.
Almost immediately I felt the benefits - it was like having a new hand!
These days I'ma bit more careful what I do with my body.