S.C.
I have heard that Formula is always harder digested than breastmilk in most babies under 6 months. My daughter was and still is very spitty. We litterally tried every formula, Similac Sensitive, Enfamil AR, Alimentum, Nutragimin - I know I am not spelling these correctly but you know which ones I am talking about. Smililac Soy etc - talked to my pediatrician and many advice nurses and they let me know that you really aren't going to see how they do on a formula unless you use it for about 1 month - and when switching it has to be gradual. If your child does have a milk allergy there is a simple test that can be done at your dr's office to test for it.
We ended up using the Good Start in the green can - we have had the best results with that one and are sticking with it.
I put her on formula at 6 months