3 week old spitting up

So my son is 3 weeks old, he is combo fed breastmilk and formula (I dont mix them together). After almost every feed he spits up, sometimes very forcefully, I try to burp him & he hardly ever burps even though I try multiple ways. Ive been sitting him up for 30 minutes after feeding but he’s still spitting up & when I lay him down all he does is cry. He was eating 4oz at a time, Im trying to limit him to 3oz every 2 hours because maybe he was overfeeding? Im going to take him to his Pediatrician tomorrow, but has anyone else had a similar issue? And what was the reason why?