Thanks for your query.
Constipation in children is mostly related to dietary intake.
In chronic constipation hypothyroidism
needs to be ruled out.
Give him plenty of fluids,glucose
water and diet rich in fiber.
Give green leafy vegetables,fruits,salads,pulses.
Decrease intake of milk.
Give honey with warm water first thing in morning.
If it persist he will need laxative like lactulose
for few days till he passes stools regularly.
Wishing your child good health.