my daughter went through a phase like this for 1 and a half weeks. she would vomit every night in the middle of the night when she would wake to nurse. she would nurse, gag, then vomit her dinner. Her doc said she was teething, swallowing her mucos at night and gagging on it while nursing. After a week I thought he was nuts made an appointment with another doc for the end of the week and sure enough a few days before the next appointment. she stopped doing it and she had a brand new shiny molar...if she is acting fine i wouldnt worry about it. If you think there are other problems then go for a second opinion. If you keep pushing your doc he is going to send her for more invasive testing. Good luck and I hope this ends for you soon!