My little one does this too. Can be 7 days before she goes for one and the couple of days leading up to that are full of loud and smelly farts (very ladylike). She's been like this since about 10 weeks old!!

My Dr told me to give her a small amount of brown sugar in some cooled boiled water but I haven't been game enough to do that! It sounds like a weird old wives remedy to me!!

Sue x