My son is 25 days old an was mostly on formula feed till now since I had a low milk supply and he had latching troubles. I used to pump breast milk a couple of times a day in addition. We restarted breast feeding for him yesterday and he seemed to be latching well .However I'm unsure if he's comfort feeding or actually getting milk. He spent at least an hour per feed but immediately started crying each time I pulled away. Is this normal ? How do I make sure he's getting enough milk and he's full?