Hi, ml,
Thanks for asking a question here, and Welcome to this site.
I am so glad you are taking her to the Vet. She might just have an infection of some sort. The Vet can tell what's wrong, with analyzing a sample of her blood.
PLEASE don't feed her table food, or human food. It doesn't have the nutrients, vitamins, and minerals dogs really need, and can do more harm than good. A good dry dog food is best. Put it down in the morning, and if not eaten in about 30 min, take it up. Put it down again in the evening.
A Pitt Bull requires a lot of exercise, and under normal circumstances, needs a brisk walk of about 45 min. every day, to release all that energy. Then, it will be hungry; if something isn't wrong with it's body functions. The Vet will be able to tell if something is really wrong.
Also, I know you didn't ask about training, but here is some information that you might be interested in:
I highly recommend a video by Ceaser Millan, a Professional Dog Behaviorist. He rehabilitates dogs, and trains people.
He has his own TV program, the Dog Whisperer, on the NGEO (National Geographic) channel, on Friday nights mainly, but also comes on some other days. This video is available from:
Cesar Millan Center
I also ordered his new book, "Ceaser's Way", from Walmart online, around $15 US, and it's very good!
There are other good videos available on the web, but this one is really worth your attention.
I do wish you and she the best at the Vet's. good luck.