Mommys bliss brand makes something for constipation

She will poop. 3 days is no big deal. Breastfed babies can go a week or more without a bowel movement. She's probably just using all the nutrients up and doesn't have much waste. My son went 5 days without a poop last week. And then he pooped twice in a day and it's been normal every day/every other day since. My friend's son only poops about once a week and that's normal for him (EBF, 7 months old). If your daughter seems uncomfortable or is straining then she could be constipated. In that case, contact her pediatrician