Hello Harish and thanks for the query
I have read your mail in detail and wants to help you out. In my opinion you must go for Stool culture examination and than take the antibiotic according the report. Take those drugs which are sensitive to the organism and in proper dose by consulting your doctor.
In addition to this keep your child hydrated, give him electrolyte powder, Give only boiled water or RO filtered water. Also give only light or semi-liquid food which is easy to digest.
Can give Paracetamol
in case of fever
and pain. Other give symptomatic treatment by consulting your doctor till the report come.