What Causes Pain On Left Side Of Chest Radiating To Back?

Hi, I have this pain on my sternum with the feeling of heartburn. I also feel the pain on the left side of my chest extending to the upper region of my back and straight down below my armpit. The pain also affects my left arm with the feeling of numbness. I have been to see the doctors and I have been given drugs for ulcer but this seems not to be working. Please can you advice