My 12 y old has had recurring d &v for 3 weeks and 4 times . first eggy burbs , diarrhea and then she will wake and vomit. she is fine inbetween ?

Possible infections: It is still posible that she has some type of infectious agent causing these bouts. Some of the infections that could produce these types of symptoms do have life cycles whee they flare up on a regular basis. Start keeping accurate track of when she has symptoms, and then when you have that data talk to your doc about whether further stool testing might be in order if symptoms continue.