My Son Is 2.5 Years Old.last 3days He Is Complaining

My son is 2.5 years old.last 3days he is complaining about abdominal pain and he had high fever, vomiting and he does 3 to 4 times slimmy n watery stools in a day..i went my pediatrician he prescribed nicetomal for fever and z&d syrup.but still he is not proper well.he is not eating anyting and stools same as earlier.what should i do.body temp is normal as giving medicine.