baby throwing up too much from formula!

So baby has been using formula they started with blue top similac, then orange now he's on the one for spit up, my poor baby throws up so much I burp him and make sure he's all done he eats the amount he's supposed to be eating, he never goes to sleep with out being burped I tried different bottles with him and nothing works he still throws up a lot, I told his dr but she continues to say to keep trying the milk, what can it be? If it's not the formula, never been thru this with my other kids, someone pls give me some advice other than ask the dr because she keeps telling me the same thing.