Hello dear, based on your history it looks like you suffer from:
1) A heart related condition: Although this is not the first cause i am thinking of, but i put it first because we would like to rule that out first by doing and electrocardiogram and probably a
stress test, preferably as soon as possible.
The other more probable cause could be:
2) Gastritis (acidity/
heartburn)- this could be caused due to eating oily or spicy food.
3) An ulcer in the stomach or duodenum could also cause the same.
4) Gastro Easophageal Reflux Disease: Sleeping with the back slightly raised (with a couple of pillows under the back) would help in this condition.
For all three above non urgent causes, you will need to avoid spicy and oily food. Have bland diet. Preferably two hours before sleeping. Additionally antacids, and tablets (
proton pump inhibitors). If symptoms don't improve I suggest an abdominal
ultrasound and probably an upper gastrointestinal endoscopy to look out for the ulcer,
hiatus hernia etc.
Hoe I could answer your question. Wishing you good health.