12 day old growth spurt?

[OurVelocity]

Hello!

My 12 day old DS has not been settling since he was 9 days old - his three hour naps are now out the window and he's constantly feeding (we're breastfeeding but with a shield due to flat nipples).

Is it usual for a growth spurt to last 4 days?

He sort of sleeps after an evening cluster feed which lasts until 2am but I'm so worried he's not getting enough milk (although the shield is full of milk after he un-latches)

I'm getting really upset and out of ideas :( I'm trying to keep calm but it's worrying me he's not getting enough sleep or food? Sorry if this has been posted to the wrong place. Many thanks.