Constipated stool with bad smell -
3 year child sometimes do have irregular stool habits leading to Constipation. Discipline her Potty timing
If problem persists - Use Stool Softener/ Lactulose
Next Steps
Bad smell can be due to infection if other factors ruled out. If persist may need Stool R/E
Health Tips
Try lukewarm milk at night time
Increase her Fluid intake