3 week growth spurt ...?

I'm not sure if my 3 week old baby is going through a growth spurt.
 For the past two days, she has been feeding at night from 10pm-4am. She sleeps only fitfully during those times, and wants to be on the boob. However, during the day, she's been sleeping for 3-4 hour stretches without waking to feed. So is this a growth spurt??