you should honestly take your baby to the doctor. it might be something wrong.. always make sure.. might possible be the babies bowels are locked up.. really get that checked out..
If you are breast feeding then your baby should be pooping 2 or more times a day. If you're formula feeding at least once a day. You should definitely take her to the doctor! Babies get constipated a lot early on. You can buy some baby lax, or those things you stick in their bottom (cut it in half!). That should help almost immediately!