Your son most likely has a bacterial infection and needs to be treated with an antibiotic. Start Syp Oflox (50mg/5ml): 7.5ml twice daily for 3 days
Add Syp Zinconia 5ml once daily for 2 weeks. Give him sips of ORS to prevent dehydration. Avoid yakult or similar brands.
Next Steps
In case blood in stools persist, contact you doctor.