Spitting up

Courtney
Okay so my 3 month started out out gerber soothe and she done okay on it for a little while then started spitting up everything so I switched her to soy, and she done the same thing, she was fine with it at first but spitting it up. So I talk to her dr and she told me to try a little but of cereal in it and again she has done the same thing. I have no clue what to do!! Anybody had this same problem?