What Causes Left Side Chest Pain With History Of Heartburn?

I began having left sided chest pain about 3 days ago. It woke me up from a sleep at about 4 am. It comes and goes. But when I do have it, the pain will last for hours at a time. It feels as if someone is squeezing my heart. A very deep dull pain. My 12-lead looked good. I am a paramedic and ran one on myself. I have had heart burn in the past and this is nothing like it.