Grabeng Paglaway / Ayaw magpa burp ni baby (3 weeks old)

Good PM po mommies. I want to ask about certain issues with regards to my 3 week old newborn. -When baby is awake/asleep, he has lots of saliva that sometimes inuubo na siya. 2. Baby doesn't want to burp after reaching 3 weeks old. Before, 1-2 weeks he is fine but now he cries and tumitigas body niya sa iyak whenver we try to make him burp. He also has a lot of milk discharge from this mouth kasi pala dede siya both breastfeed and bottlefed (Similac). Ano kaya pwedeng gawin kapag ganito mga mommies? Salamat po