Another possibility is that you may be suffering from pain from the intercostals, an internal and external group of small muscles attached to the ribs.
These tiny muscles can cramp after surgery and cause pain like you imagine a heart attack to be, and even hurt so sharply that you physically can't take a full breath because it hurts so much to expand your rib cage. Intensely painful, but not harmful.
This is added to the fact that your ribs are laced with nerves (that's why it's a favorite tickle spot). Get cranky muscles and nerves together, and you have pain soup. It's possible pain from it can linger, if the muscles are unhappy.
However, an attack of that that should normally be temporary (minutes, not days), and you should be able to breathe normally before and after. Your inability to take a full breath may well be attributable to liquid building up in the pericardium around the heart. That would at least require steroids, if not actual removal.
Plainly, with that kind of pain, you want to see a physician to be sure it's not anything that needs professional attention.
Best wishes,