My son is now 12 but used to spit up as a baby. The doctor diagnosed it as reflux. He perscribed Rigalin (Not Ritalin). It empties the contents of his stomach faster so that small meals throughout the day are what he would have rather than spitting up after each meal he managed to keep everything down. Once he grew to about 5 he had no more trouble with it. It would only occur after running in gym or excessive excercise like football. The valve that seperatd the stomach acid from the esophogas would stay open and release fluid and as a child they do not know how to control it.
As a result this also seemed to speed up his metabolism the frequent small meals. He was somewhat of an overweight baby prior to the riglin and diet adjustment. He may also be lactose intolerant but only slightly. There is a few formulas out there for babies who spit up frequently that are a mixture of milk base and soy base. I use Gentlease Lipil which is for gassy babies but I noticed it states it is a combination of both soy and broken down lactose proteins.
I know I saw one for babies who spit up frequently as well but can not recall which one it is is but it is made by the company that make Lipil. Hope this helps you.