Spitting Up Problems

[SilasLove]

So my little guy started out on Enfamil Premium, which is just a regular formula. After spitting up became an issue the doctor switched him to Enfamil Prosobee, which is a soy formula. He was doing OK on it, but spitting up was a normal affair still. So, I started putting a little cereal in with every bottle to help thicken it so it would not be as easy to spit up. That worked for a few weeks, but now he has started spitting up a lot again. And I mean a lot when I say a lot.

I just do not know what to do now... can anyone help me out? What is the problem, why does he start spitting up large amounts after a few weeks of being on the formula?