Reflux help!!! 5 week old son.

My son is drinking Enfamil Gentleease and has been fine on it up until the week. He started puking almost every feeding so I took him to the doctor. My son keeps gaining weight which is good. At 5 weeks he is 10 pounds so he suggested I switch to a similac spit up formula and to try pedialite. Well today most of the baby's feedings went much better until night time and he puked for every feeding and was super fussy. I gave him an ounce of pedialite and he spit some of that up too which the doctor said if that happened he might have stomach issues. Anyone go through anything similar and have any advice??