Thank you for your query,
Your child seems to have persistent diarrhea
as there is weight loss
In persistent diarrhea in addition to infections, other causes of diarrhea like excessive consumption of carbohydrates, lactose and sucrose intolerance, excessive consumption of fluids and juices to be ruled out.
Restrict fluid content to less than 90 ml/kg/day.
You can try lactose and sucrose free diet after consulting your Pediatrician
Stool to be sent for routine and for culture.
Withhold milk for some duration and try to give more solid food.
Consult your Pediatrician to for evaluation.
Hope I have answered your query.