When did your baby sleep through the night?

K

At how many weeks did you all start letting your baby sleep longer at night? My baby is almost a month old and I'm still waking her up to feed about every 3 hours - mostly because she needs a diaper change very often and she never cries when her diaper is dirty. She's gained a good amount of weight, and the pediatrician said it was okay to let her sleep longer, but I feel weird about it.