Hi I understand your concern. For weight gain have heavy dinner comprised of whole cereals, like wheat, oats, Dalia, rice, ragi, barley, jowar. Have milk shakes n fruit smoothies, milk and it's products, soyamilk, dal, if non veg then eggs, fish and lean meat. Keep yourself hydrated.
Next Steps
Check any hormonal issues you having or not.. You can consult personally for customized diet plan,online through us.