Hi there -
My son, now 5 months old, had and still has the same problem. For us it is definitely reflux - you should talk to your pediatrician right away b/c our baby needed to be on meds for it. He started on Zantac and now takes Prevacid instead. Also, we went through the different formulas as well - Similac Advance, Similac Soy, Nutramigen - nothing worked except for Alimentum. I recently tried the Nestle Good Start, but he spit up more with it (almost no spitting up with Alimentum), and I kept finding little strings of what looked like part of the can inside the Good Start can, so I refuse to use it anymore. I also read the labels on the store brand formulas that are supposed to compare to Alimentum, but they seem to have more vegetable oil related ingredients as opposed to milk ingredients - I just feel safer using Alimentum. It is defintely a bigger expense, but worth it to us. (Also with the Good Start, yes it costs less, but the scoop is twice as big and you use just as many scoops to mix it, so not real sure there is a ton of savings there.) We did end up taking our son to a specialist, who really didn't help much except to say to try Beechnut infant rice cereal in his bottle (they consider the Beechnut to be hypoallergenic, other brands aren't) - this helped a lot for a while - definitely decreased the reflux symptoms, but now he refuses to have the rice in his bottle. He will eat it from a spoon, so we do that now instead.
One thing to think about as far as the added expense of the Alimentum - we were told by every doctor that our son should eventually grow out of this - usually by 6-12 months. Hopefully the added expense is only temporary and he can eventually switch to a less expensive formula (or milk when he's old enough!).
I know firsthand how hard it is to watch your baby suffering through this - I really hope you find the solution that works for you!! Good luck -
J.