hi Bec, going for 5 days without a poo is perfectly normal for a breastfed baby. My sister's DS once went 10 days and the nurse wasn't really concerned. Constipation in babies is more about the texture and consistency of the poo rather than how often they do do it. If your nephew is doing poos that are soft and he isn't straining then they're ok. If he's straining and his poos are like hard little pebbles the he's probably contispated.