Thank you for your query,
Your child may be having diarrhea due to a virus or antibiotic associated as child is receiving the amoxicillin
Maintain his hydration.
Give sips of oral rehydration solutions like Pedialyte to replace the loss of water in stools and to prevent dehydration
You can add probiotic
like econorm orally as to restore the normal gut flora and which is very useful in antibiotic associated diarrhea.
Consult your Pediatrician
along with the stool report for correlation and for the appropriate management.
Hope I have answered your query.