What Causes Vomiting In Baby While On Formula Milk?

Hello, My baby is 4 months and 10 days old and weighs 6 kgs.He is on breastfeed as well as formula as I do not have sufficient breastmilk. I started giving him Nan pro 1 when he was 1 months old and is continuing the same. My baby vomits a lot , about 10 - 15 times daily since birth. His paediatrician says there is nothing to worry about as it is very common. But i am really worried about his vomiting problem. He vomits thick curd like substance and is asking for feed most of the time. I prepare formula using 4 scoops of Nan pro 1 and 120 ml warm water. Is the preparation ok ?and is the formula sufficient for him ? Please help.