About every 2 to 3 months I get a muscle tightening and moderate pain on & under my left shoulder blade that slowly eases up after about 4 days or so while taking motrin and using back massager pad on and off throughout the day and evening. I don't have to be doing anything strenous. I could just be bending down or even just getting out of bed in the morning. The first day is bad as I have to take shallow breaths due to pain. And it feels better when I stand then when I sit or lay down. I finally went to see my doctor and after taking x-rays, he found nothing unusual but I don't know why this would be happening over and over again?