Thank you for the query.
First of all you should have gastroscopy to see stomach condition. Your symptoms can be caused by stomach inflammation
, Peptic ulcer or even stomach cancer
. B12 and folic acid deficiency
can be a part of stomach inflammation (called Addison-Biermer anemia
Other common reasons of being gaseous are chewing gum, smoking, drinking carbonated drinks, loose dentures, chronic bacterial infection. Inflammatory bowels disease should be also considered.
I suggest you to have gastroscopy done, than stool tests, abdominal CT with oral contrast (enteroclysis).
Hope this will help.