Sounds like a bit of wind pain. When Caleb went 8 days between poos (I wish now lol) he farted quite a bit like how you've described.

As long as when he finally does one it is soft. Usually when they go a few days the consistency changes from runny and mustard seed looking to that of smooth peanut butter but still quite soft. If it's hard, dry or little pebbles then it is constipation.