I get shoulder pain, left arm pain, back pain and heartburn. I'm worried about a heart attack. It happens every day though. What could it be?

Multiple. Many things are possible, but the heart attack will harm you the most. See a doc, get thatruled out, then they will look for stomach ulcer, gerd, esosphagitis, herniated disc in neck, etc.
Doubt heart attack.. At your age. Could be esophageal, musculoskeletal, neurologic. Stop smoking, drink less, see md.