For the past few days, i've had an intermittent pain of varying intensity that seems to start about 5 inches to the left of the bottom of my left shoulder blade. (therefore, more of a side pain than a back pain.) occasionally, it will radiate from that area right through my left breast. It starts as a somewhat sharp sensation, and tapers to a dull ache, lasting only a few seconds. I cannot determine if this is muscular in nature, or because of the location, could it be lung related? Thanks for any help/advice!