6 week old sleeping all day, not eating

So my baby’s gonna be 6wks tomorrow and today she has been sleeping all morning. We woke up at 7:30am and shes been sleeping on and off since 8:30am. Hasn’t fed much. I keep trying to put her at the breast or giving her a bottle but she takes a few sucks and falls back asleep. Its now 1pm and she barely has eaten anything. Should I be worried? What should I do? Is it a growth spurt?