Maybe BB is not enough water , so BB cannot 屎屎, Normally, BB have 屎屎 after they have a milk. If not, 1 - 2days it doesnt matter (hospital told me).
You can try after milk, to give BB some water.
To let BB inside , more smooth then 屎屎.
Or between milk & milk, you also give BB some water. It doesnt matter how much BB take.
My son also has problem when he's BB. Everytime he's very hard to 屎屎, sometime have a little blood, or few days has 屎屎. If he is no over 5 days, I will use med to insert pet pet (take from hospital - body checking).
Everytime he 屎屎 , he will cry very loudly.
Now , he is 3 years old.
Next time, when you go to hosptial & health clinic for checking. You can ask nurse or doctor (status - BB after injection.)