What Causes Vomiting And Diarrhea In An Infant?

hi, my 1 year 4 month baby boy have a diaherra from last 18 days. at first 1 week vommiting was there. we went to doctor and giving him all medicines but no use he is suffering a lot. i am not giving him milk and any other varities of food other than rice,khichdi. what should i try now?