Allergic to breastmilk

Is it possible for my baby to be allergic to breastmilk/lactose?  She is 2 months old and has always had issues with gas, vomiting and just overall always having an upset stomach.  I have completely cut out dairy from my diet because that seemed to give her the most issues.  I have had to supplement with formula occasionally and she projectile vomits with regular formula I have tried soy based formula and whenever she drinks that is the only time she seems to be content.  I would love to continue breastfeeding but I feel so horrible watching her in pain every time she nurses.  Has anyone else had a similar issue or have any advice?  She has an appointment with her pediatrician on Friday.