How much spit up is too much?

My 2-week old baby boy is eating both breast milk and formula. He was given regular Similac formula at the hospital but then changed to the Pro- sensitive Similac a few hours later because he was spitting a lot up. He has now started to spit up a lot of the formula I should say he eats about a 2 oz bottle every 2 1/2- 3 hours. Should it be changed again or is it normal for him to spit so much up? Also, im wondering if it has anything to do with the lactose since im lactose intolerant could he maybe be?