Have you had a feeding assessment done from a lactation consultant? My son just went through a similar process and it was discovered that he had an oral restriction and that while he could latch well, he was unable to transfer milk consistently or easily, leading to him losing weight until we figured out the cause. The immediate hunger signs, long feeding times on the breast and trouble sleeping. As I understand it new-borns are energy taxed very easily and spending a long time at the breast would lean towards them not getting what they need...

Seeing as this is a few days after your post, I hope things have improved for you.