I think firstly that this is a practice that varies wildly in different cultures. In the '
First world' we leave our babies in nappies a lot longer than in developing countries. We have lost the knowledge and/or motivation to get our kids out of nappies early.
We all have expectations of our babies and this is one of the biggest issues we face in childrearing.
To Wewei. your baby's digestive system will change quite a lot as you introduce solids. In time you will find a new rhythmn to his bowel movements. Just be patient with him and it will all settle... Good luck