Hi there
Congratulations on your baby.
It is not uncommon for breastfed babies to have several days without having a poo. Some will go a week or more - even up to 2 weeks! This is partly because breastmilk has very little waste. This isn't a problem as long as the poo is soft when it comes out.
Is it possible her problems are because of air in her body (gas, wind)? This is often very difficult for young babies. Are you able to make her burp? If the problem is because of air we may be able to make some suggestions to help you.
When is the last time she pooed? Why do you feel worried?