Fussing and pulling off?

My son is 11 days old and has been nursing great all week but starting yesterday we’ve been having a lot of trouble. He fusses constantly while eating, and pulls off over and over again even though he’s still hungry, and he’s spitting up way more than ever before.

We use a shield and have since day one, But I’m not worried about him not getting enough through it because every time he pulls off he has a bunch of milk in his mouth and it gets all over his cheeks. Could it be too forceful of a letdown? Or reflux?

I’ve tried putting him at a more upright angle and it helps a tiny bit. Also tried a little gripe water beforehand, and attempted burping him whenever he pulls off crying.