With loose motions since last week,your son would be dehydrated.First step is to rehydrate with electrolytes,ORS
solution,famous Salt-sugar water or any other rehydrating fluid.
He should take an easily digestible,light and fluid diet.
Watch out for anaemia
,exhaustion and weight loss
It may be Piles or other diseases oof intestine.
Treatment will vary according to cause found by Doctor.