no milk for new born all of a sudden

My son was born on April 11th. Till day before yesterday I had milk probably that was sufficient for him as he was peeing and pooping frequently and it was normal. From yesterday I see drastic drop in my milk and he is not satisfied how much ever I feed him. He didn't sleep whole night and was hungry all the time. I spoke to paediatrician who will be on emergency and he asked me to give nan pro if I feel my milk is less. I tried feeding him again in the morning, but he is sucking just as a pacifier, but not swallowing anything. No pee or poop from early morning which indicates that there is nothing in his stomach. Pls help. Has anyone faced it? What causes sudden drop in breast milk. How to increase it?