hi ,welcome to HCM
i understand your feeling
seems he had viral infection with loose motions(GE)...
let me know detailed history about his general status..did he has fever,diabetes or hypertension
,how is his urine frequency and output,pain abdomen,
investigations,were they normal,usg abdomen..
due to acute severe dehydration
and electrolyte imbalance
it can cause severe weakness for few days and they dont feel like eating ,nausea can last for few days,,indigestion
due to loss of flora(useful bacteria in gut for digestion..
i suggest you not to worry and give him good healthy diet which includes
fruits,vegetable soups,coconut water,high calorie diet,multivitamin
tab,sporolac or econorm sachets.etc
inspite of these measures if no improvement ,then
consult a dr ,get general examination and follow the orders..