Hi, C.!
Seems as if a LOT of us have had different issues with our babies spitting up (beyond "normal"). My 16-year-old was on Enfamil, and when he was between 3 and 6 weeks old, he started throwing it up VIOLENTLY (and it was a strange shade of green, too!). I had him in the hospital, because the dr didn't know if it was "just" an allergy, or if it was a symptom of a problem with his single kidney. I switched him to ProSobee, and he did ok on that....for a few weeks, then he started throwing that up. I switched him to Good Start, and he did GREAT the rest of the year! (He was OFF his bottle ON HIS OWN the week he turned a year old! No such luck with #2. LOL) He was funny when it came to being able to eat/drink dairy. He could eat any cheese, yogurt, frozen yogurt, or mac 'n cheese made with the cheese sauce (but not the powder that you mix with milk), but he could NOT drink milk, or eat pudding of any kind, or ice cream. Those items gave him INSTANT diarrhea that took "forever" to get cleared up.
My 2-year-old has had different issues....His vomiting wasn't nearly as projectile as my older son's was, but he was spitting up an awful lot, and he cried a lot more. We ended up trying 7 (that's right...SEVEN) different formulas for him! The one we ended up on wasn't the most expensive, either! (go figure that one...) Enfamil had just come out with their A.R. formula in the summer of '05, and that's the one that did best with my little one's stomach.
As far as questioning allergies and illnesses going around, the pollen counts are really high right now, so ask your pedi about starting your kids on something like Singulair and/or a nasal spray. Our pedi had the little one on Zyrtec, but our Ear Specialist said to quit giving it to him...He said Zyrtec is great for treating the allergies, but it also has a nasty tendency of messing up the kids' ears and their hearing. He sees a lot of this with his pediatric patients. I also have "outdoor" allergies, and they are really bad this year.
When your baby gets closer to being a year old, and you're ready to take him off his formula/breastmilk, you might want to consider alternatives like rice milk or potato milk. I'm reading a book on Autism spectrum (my son has PDD-NOS) that recommends these types of "milk" if you suspect a milk allergy or lactose intolerance. (Info just to let you know that there are alternative forms of "milk", besides soy.)
Congratulations on your new baby! Feel free to email me if you have any questions, and I hope I didn't scare you with our story.