Try taking him from the breast every few minutes to burp him/her if baby is a good eater he is probably taking in a lot of air ..Also be careful about anything strong you are eating or drinking I knew one mom who loved apple juice and drank a lot ..baby was consistently throwing up. If it continues maybe speak to the pediatrician as projectile vomiting is a sign of pyloric stenosis . Congratulations on the birth of your baby I am sure he will settle into a good feeding pattern soon .
it could also be from heavy let-down. If your breasts feel very full or are leaking try to manually (not with pump) express just a bit. Ie, if I was too full I would have a steady stream without applying pressure once it dwindle down to a drip without pressure then have lil one latch on for feeding. Usually the first few days I had to do this and then just after the growth spurt during start of baby food. Hope that helps! Congrats!