Hi,

It is really uncommon for breastfed babies to get constipated. True constipation involves hard, dry poos. In the early days it's more normal for babies to have several poos per day - it can almost be at every feed. Usually the poos are runny/mustardy/ seedy/grainy or pumpkin soupy - really the colour does not matter much as long as their are plenty!
Around 12 weeks things can change and some babies can go a week or two without a poos - but when it comes - stand back. It is still usually runny and a variety of colours/consistencies. There can be quite a bit of grunting involved even for these soft poos - but there is no problem.
It's important to get a handle on the way baby poo changes - because lack of poos in the first few weeks can be a red flag to indicate baby is not getting enough milk. If this sign is picked up on, and mother seeks assistance then baby gets enough breastmilk and it can all work out very well