If she is not eating, did the vet tell you to give her nutrical. You mentioned her head jerking. Makes me think she may be having a hypoglocemic episode.
Do a search here on YT. There is alot of great information here.
Also look at the thread that was started for new people it also has great information. The link below will take you there, just click on it.
http://www.yorkietalk.com/forums/sho...ighlight=amber