It's perfectly normal!
Exclusively bf babies can go 1-2 WEEKS without having a BM and it's normal.
Breast milk is
so digestable that there is often very little waste. It's all used by the body with very little left over.
So don't worry! Just be thankful you've had a few days off from changing poopy diapers!
FYI... Constipation refers to BM that are hard and difficult to pass. Having infrequent BM does not make one constipated, as long as the stool is soft and easy to pass. It's only if the BM is hard, pellet-like and painful to pass that the term is correctly used.