My baby have not poop since for 4 days. She is currently 4 months old and is exclusively breastfed. Is it something to be worried about? I'm really worried.

You can feed some probiotics to your baby to improve his digestive system. BioGaia has probiotics suitable for young babies. Also, do help baby to massage his tummy to ease the constipation. You can refer to this sample video on how to do the massage. https://www.youtube.com/watch?v=RWFg0ODAQvE