Welcome to Healthcaremagic.
From your query, I suspect you may have Gastroesophageal reflux disease
But some other disease like celiac disease
or irritable bowel syndrome
can cause bloating and belching sensation.
Gas in stomach and flatus can be easily avoided by changing your eating habits and timings.
Gas in stomach is usually due to air which you swallow and also by bacteria which produce gas by breakdown of foods.
You can easily avoid gas by the following methods.
Eat foods slowly, Avoid smoking and chewing gums.
Avoid carbonated drinks and Baked and packed foods.
Chew with mouth closed.
Sometimes beans, fatty foods and sugar substitutes can cause gas.
In addition to these you can take the Pantakind DSR.
It does not have major side effect.
It may cause headache and diarrhea.
Long term use can cause Atrophic gastritis
I advice you to do some basic investigations like Upper Gi endoscopy
and H.Pylori test to rule out any ulcers in Upper Gastrointestinal tract.
If h.Pylori is present better take H.Pylori kit drugs.
Hope this helps.