Why does my baby vomit milk?

My baby does not like my milk! He throws up after I feed him and I don�t mean spit up, I mean projectile vomit. In hospital he had low blood sugar issues and had to be formula fed. He was formula fed for the first few days of his life and never spit up at all. As soon as I started giving him milk he started puking. I dont eat anything spicy or anything so what can it be. After several episodes with the throwing up after milk I gave him formula last night and he was fine. I thought milk was easier on a baby but that doesnt seem to be the case with me. Any thoughts on this?