Hi,
For constipation
Reduce milk And biscuits
Toilet training
Make him sit to pass stools daily
Give green leafy vegetables and fruits
Give plenty of liquids/ water to drink
Next Steps
If still hard stool, give Syr Duphalac
For weight
Make food calorie dense by adding ghee/butter
Add vegetables in non- veg , if he loves non-veg
Give Syr Zincovit( multivitamins)