Are you suffering only from the past one month or had faced in the past?
It could be gastroesophageal reflux,you need to take antacids but need to do some tests as your age is 78 and more history and details of your present condition is needed to correcty assess
Next Steps
Can try antacids like PROTERA D CAPSULE before breakfast every days for 10 days and should see if acidity resolves,if not need to perform some investigations
Health Tips
Try to avoid Tea,coffee,soft drinks
Try to avoid Junk,spicy food
Take curd,buttermilk
Have plenty of oral liquids like juices (try to avoid citrus fruits)