This is DR. David
where was this stone you had 20 years ago? a kidney stone or gall bladder stone?
your symptoms sound more likely to be from excessive stomach acid which can cause acid reflux, heart burn, belching, sore throat, sour taste in the back of the mouth
certain foods can worsen stomach acid like alcohol, spicy foods, oily and fatty foods, fried foods, sodas, tomato sauces, large meals, sodas, black pepper. you may have to change your diet to avoid these
these are also stomach acid reducers like maalox or mylanta or zantac or prilosec which can help decrease stomach acid levels.
have you tried any of these over the counter stomach acid reducers before?
what do you eat regularly?