3 month old hasn't💩

Mom • My name is Raschel. I`m married and have a wonderful 4 year old son and a beautiful rainbow baby girl born nov 2016.
I know it's normal for breastfed babies to go without pooping for a while. My 3 month old is formula fed and hasn't pooped in 6 days. She doesn't seem to be in any discomfort. Should I be worried? Thank you!