first child. It wasn't until our 3rd or 4th child that we became aware of the book, and it made a world of difference. It talks about how to calm a baby down and why they need it. A lot of it is wrapping them REALLY tight, and if they wiggle loose at night, they'll often wake up. And also white noise

Otherwise, it's just keeping at it. Realize there is a "4th trimester" for humans that is outside the womb. Your baby is still in the fourth trimester---they're technically still a fetus. So they won't sleep like a human yet. This is why 12-week paternal leave is important.