Breastfed babies are less likely to get constipated like formula fed babies do.
However still even breastfed babies can and do get constipated just like formula fed babies.
If the baby is old enough to drink some prune juice you can give the baby some prune juice to help relieve the breastfed babies constipation.
You can also massage the babies stomach and work their legs back and forth like you're pedaling a bicycle.
Feeding the baby some applesauce or other pureed foods that are high in fiber can usually get the baby over being constipated.
If the baby is still constipated after a week then you should take the baby to the doctor to make sure nothing more serious is wrong.
You can also give the baby some apple juice for constipation and just put the apple juice in the babies bottle and allow the baby to drink down the bottle of apple juice.
After awhile the baby should start moving it's bowels again and pooping again.