My 7 year old female pitbull has been throwing up off and on for 2 weeks took her to the vet antibiotics arent helping her stomach is swollen negative xrays of the stomach low wbc negative biopsy in the fluid that was drained barely eating drinking l?

I hope that a full blood panel and ultrasound was performed on her to rule out liver disease, cancer and heart failure. 

It is important to know if it was a particular WBC that was low, or just an overall decrease in the WBC's as a whole.  Certain WBC's have their own diseases associated with abnormal numbers of them (be it low or high numbers).

For instance: A low lymphocyte count combined with low albumin levels (this would be seen on a "full" blood panel) a swollen abdomen and vomiting may point to a more rare disease such as protein losing enteropathy.

The above afflictions (hopefully your little girl does not have anything serious like these conditions) are not cured by a simple course of antibiotics.  Since she isn't getting better, it may be in her best interest to "push" her veterinarian into digging a bit deeper into the cause of her discomfort.

Obviously these things can only be diagnosed by your veterinarian, however, it is good to be informed and to know what questions and/or tests to ask your vet about in order to get your little girl on the right track.

Hoping for a speedy recovery!  Good Luck!