It sounds like he's suffering from a duodenal ulcer caused by H.Pylori. It's common enough in males, and can be even commoner in young intelligent males.
These small ulcers usually heal, then break down again repeatedly, leaving a little scar tissue which contracts, and bit-by-bit narrows the pylorus- the exit from the stomach into the duodenum (small intestine).
This causes the regurgitation of acid and stomach contents. It is a chronic condition, usually persisting for years, unless it is treated. Happily, these days the condition is easily treated without surgery. Meantime, Ranitidine or Omeprazole will help considerably. H.Pylori needs to be cleared from the stomach first - a short regime of antibiotics.
However, the condition needs to be investigated first, to exclude other causes. A barium meal (X-ray) will reveal any ulceration, or whatever.