What would you do in this situation?

Your son is three months old he has been to a hospital for projectile vomit. Severe not spit up actually hitting the wall across the room type. You were following doctor advise and you tried every formula that had been made at the time. The specialist only response after they put probes down your sons throat is he is allergic to formula. Feed him what he will eat such as baby cereals and vegetables and milk that has been boiled and skimmed and a liquid baby vitamin once a day. Cps steps in and says you are abusing your child and they are going to take him the reason being is that he has gained a pound in a month but for the last three months he weighed the same as the day he was born? What would you do?