is my baby okay?

My baby is 24 days old today. I have been mix feeding him (dl, express pump and formula). Today after bf, he cried agn for milk so i topped up with formula. However, he drank only about 10-20ml before rejecting the bottle. Burped him, but he will end up throwing up whatever he drank. He managed to finish 120ml for 1 feeding today. Is it normal?