My infant has been vomiting in the morning...?

She is 9 months..about a month ago she starting vomiting, copious amounts during the middle of the night. She vomited a day later, early in the morning. About a week ago, the vomiting became almost daily. She projectile vomits...it has been a yellowish to a milky color...She typically nurses about 10-20 minutes before these episodes. I have omitted all milk proteins, eggs and soy from my diet, as she was recently found to be allergic. She had an abdominal xray, and it was negative for a foreign object obstruction. She is having a barium study on Wednesday, to rule out a malrotation...but she doesn't appear to be in much pain...at all...What else could it be? Has anyone had a similar experience?