Baby & Burping

I have a 9 day old, and lst night/today he doesn’t really wana burp anymore or I should say it’s gotten harder. He eats and falls asleep. Mind you, I still turn him over to burp him but still, nothing and he just falls asleep. I literally burp him for like 15 min sometimes more and nothing 😔 so is it crucial they burp? I don’t want him to become colic.. btw he’s formula fed rightnow but I plan to alternate with breast milk.