Thank you for your query.
The description provided by you suggests gastroenteritis
. If it is occurring every week then you need to check the source of water supply as that may be the cause.
I suggest that you get your son's stool examination done and give him medicine accordingly after consulting the treating doctor. Also ensure that he has plenty of liquids so that he does not get dehydrated.
I hope I have anwered your query to your satisfaction.
Wishing your son a speedy recovery.