vomiting?!

Okay so since my baby has been born he's had problems with throwing up. At first it wasn't that bad bc he was bfing but I changed to gentle ease bc he had colic, gas, constipated, and throwing up. Well turns out the wic nutrionist said he probably needs soy so he's on prosoybee now and he's still constipated frequently and throws up a lot. He does still have gas but it doesn't seem to bother him as much anymore. And wheh he does throw up it's not normal spit up. I do put cereal in every bottle bc if not he vomits way more. Idk if I need to switch to a different kind of formula or if he needs to go to the doctor about something that may be wrong with him. I've told his doctors about it before and they've always said as long as he gains weight he's fine but it just bothering me him vomiting this much bc I know that's not normal. If you have any advice on what I should do please share thanks