This is my third kiddo. She's 4 days old. I'm concerned because today she has literally slept all day. I wake her up every 2 hours to nurse and change her diaper, but she literally passes back out. Previously, she had been more of a regular newborn, sleeping MOST of the day and cluster feeding at night.

She doesn't appear jaundiced and she's having enough wet and dirty diapers. No fever. At what point do I get concerned?