Formula allergy? ?

My daughter will be 2 months old next week. since she was born she has had very loose stools and constant spitting up. they changed her from similac advance to similac isomil before she left the hospital, it helped a little at first but now she throws up several times a day usually after feedings, the spitting up has gotten worse and so has her loose stools he has also developed a rash on her face,chest and back. her doctor changed her formula again to a hypoallergenic one but it made the vomiting even worse so the changed it back to isomil. is it possible that she allergic to all these formulas, or do you think its something else?