Feeding constantly?

My LO is 9 days old and today she's been eating about 1-2oz and falling asleep and not taking more but then screaming an hour later for more and then eating another 2oz. She's been taking breast milk from the bottle. I don't know what's going on. Could she not be getting full? I supplement formula at night so I'm unsure about how tonight will go after this eating every hour today. I'm exhausted. What is going on?