6 Month old Vomits After Milk/Formula but keeps down Pedialyte?

My 6 month old just started vomiting 2 weeks ago. She started only once a day and has progressively got worse the past two weeks. She never had problems with reflux before and the doctor has had us switch from feeding to Nutramigen and Neocate. Neither of them have helped. She does not have a fever nor a runny nose just vomits (projectile). We have kept her hydrated with Pedialyte - she hasn't not vomited that. Now she is at the point where she wont take the bottle with milk and is starting to refuse the pedialyte. We have taken her to the ER they gave her a CT scan, stomach x-rays when she drank barium and an IV of fluids. They have no idea what's wrong. Please help - now they are talking about giving her a colonoscopy and potentially a feeding tube to rest her gut.