I have a question for the moms that breast fed. My son is a premie and his pediatric told me that my…

I have a question for the moms that breast fed. My son is a premie and his pediatric told me that my son won't be able to latch until this upcoming week to pump and fed my breast milk to him for the time being and supplement with formula if he don't get enough breast milk so I have been. Well yesterday night and today every time I feed my son my breast milk and burp him about 5 mins later he spits up so bad it cones out his nose. Could there be something in my breast milk to cause a reaction like this cause? if I feed him formula and burp him he is just fine. I feel if I give in to just formula I have failed him but I don't want him throwing up every time he eats my milk. Any advice or opinions are helpful!