I'm a 24 year old male, 6'4, about 205 lbs. I exercise (a short jog or quick work out) every single day. I'd say I'm in pretty good shape.
Occasionally when I'm jogging and going hard (even though I'm running out of breath), I begin having a sharp pain under my right shoulder blade. This has been occouring off and on for a while. After I stop exercising (i.e. start walking) the pain goes away pretty quickly. Today, right after I went hard and felt the pain, I put my hand on the pain and noticed it felt like the blood vessel/vein was pumping very, very hard.