Since 2months experience burping and gas

My husband frequently experiences excessive burping, especially at night. On one occasion, he burped continuously for almost two hours very strange.  How can a person burped for 2 long hours?? His stomach becomes bloated and full of gas, and visibly increases in size with strange internal sounds. He has consulted multiple doctors and was given medications (both allopathic and Ayurvedic). However, the relief is only temporary — symptoms (burped) return after stopping medication, and burping continues even during treatment. An ultrasound scan was done, but the results were normal. An Ayurvedic doctor prescribed 15 days of medicine, which did not improve the symptoms. Some days he feels completely fine and at times he suffers. I observed having boiled food during his issue helped him to lower the symptoms(burbed) The burping is more frequent at night but not everyday. In these two months his symptoms come n go. Please suggest what best I can do?