Thanks for your query.
Your baby is having diarrhea which could be viral or bacterial in nature or could be drug induced as diarrhea is common after amoxicillin
Continue with pedialyte
after each loose stool
Give coconut water,buttermilk,curd,boiled potato,rice porridge.
Give lactobaccilus for 2 to 3 days and zinc for 14 days .
Keep his bottom dry and apply calamine lotion 2 to 3 times a day.
Wipe area very gently.
In case symptoms get him evaluated by pediatrician
Wishing your child good health.