6 weeks, is he feeding enough?

Marisa

He drinks formula maybe every 4 hours, 4oz.

But in the evening and night he goes about 6 hours without eating. Then falls asleep again and goes another 6 or 7 hours. I'm very grateful for the sleep but should I be waking him to eat.. or worried he's not eating enough?! My mom said he'd wake up screaming if he was truly hungry.