What Causes Pain In Between The Shoulder Blades Radiating To Left Arm?

I am a heart patient and have been having chest pain if i take a nitro it goes away but comes back with movement my appetitie is poor i have pain in mh back between my sholulder blades and radiates down my left arm which becomes numb and tingly i feeel short of breath and i use my nebulizer but it seems to help for some. but nmot much i am lightheatheaded and dizzu i feel a crushing feeling on mu chest