hi welcome to HCM
-i had gone through your query and understand your concerns. i would come up with the possibility of IRRITABLE BOWEL SYNDROME
is the cause for his sufferings.
. People with IBS
have a lower pain threshold to stretching of the bowel caused by gas or stool compared with people who do not have IBS. The brain may process pain signals from the bowel differently in people with IBS.
-genetic predisposition often run in families
I hope this is helpful for you, thank you