I had what I thought was a heart attack - pain mid-sternum - after a bad wreck in which the seat belt and airbag hit me mid-chest hard. I'd had a heart attack a few years before, and the pain was in exactly the same place. I just didn't have the radiating pain down the left arm. It turned out to be a hiatal hernia - seen on CT scan. The eating too much might be the clue.
Of course it COULD be heart-related, so see the cardiologist first. I get pain from arrhythmias and tachycardia episodes too. But if it's not that you might get a gastroenterologist to check you out. The gastro might want to do an endoscopy - looking down your throat - but that's not always the best way to see a hiatal hernia. I'd ask for a CT or a barium swallow.