Hi mama, 3 days is quite long for a formula-fed baby, most of them usually go every 1-2 days talaga, so I'd suggest checking with your pedia to rule out constipation, especially if she seems uncomfortable or her tummy feels hard. A few of us moms noticed na sometimes ang formula brand or water ratio can affect pooping habits, pero it's better to have a doctor check muna to make sure everything's okay with her digestion!