Here in the States most pediatricians don't worry about diarrhea until it's lasted for TWO WEEKS. (I don't know about you, but I'd be INSANE after two weeks!) As long as your baby isn't getting dehydrated, just let his own system work through it. Make sure you give the Diarolyte as prescribed, that will keep his electrolyte levels up and reduce the chances of dehydration.
Babies digestive systems are still developing, so sometimes diarrhea is just a matter of course. Be patient, give baby and mum lots of love and it'll work out.