Questions about baby formula?

I first started feeding my son similac advance. He was drinking it okay just had problems having a bowel movement so i switched him to gerber good start, now he is having problems with spitting up but didnt have problems before with similac so i dont think he is lactose intolerant. What is a good formula for babies with gas a spit up gerber good start was suppost to be but it made him even worse any suggestions.