Thanks for posting your query.
With the available described symptoms, there appears to be possibility of tropical sprue
or Irritable bowel syndrome
Is he getting relief in abdominal pain after defecation?
You should consult with internal medicine specialist/ gastroenterologist and should go for thorough check up.
You should go for complete blood count
, thyroid profile, endoscopy with duodenal biopsy and colonoscopy.
Irritable bowel syndrome is a functional disorder
of gastrointestinal tract and usually diagnosed when all relevant investigations are in normal limits.
You should continue probiotics and take rifaximin and selective serotonin reuptake inhibitors.
Dr. Mayank Bhargava