What Causes Pain In The Shoulder Blade Radiating Towards Armpit And Chest?

I been having pain in the middls of my shoulder blade and spin and i get pain under my armpit to my chest. It starts from tje back off my armpit my doc cant find anyting its my left arm haf it for 4 year now and now my right arm is starting to. I also get mtightness un my chest with pain wen bend dawn and tigh my shoes and den i get up and strech tats wen i feel tightness with pain