Thank you for the query.
As the symptoms last longer than 48 hours and he is not improving you should definitely take him to the doctor. The most common reason of his symptoms is bacterial infection. Please do not wait any longer. He should have stool test
, blood work and abdominal ultrasound
Antibiotics might be necessary. You can also start probiotic
intake. Try to keep him well hydrated as fever
makes him loosing liquids quickly.
Hope this will help.