How To Control Watery Diarrhea In An Infant?

Hi, I ve got a male baby who is 3 months old now. He is been passing watery stools more than 8 times since 8 days.. when diagnosed, the Dr says nothing to worry as it is a acute diarrhea. He has got his stools examined for mucus - present and pus remains 3-4/hpf. He is active, breastfeeding, not looking weight. But his anus area is too reddish. What needs to be done to control this?