[poo poo's mom]

I have a 2 1/2 yr old yorkie, she weighs 3lbs 5 oz, I have never had any problems with her until yesterday. She has not eaten anything since Friday, she is drinking water, but she is throwing it up. I took her to the vet 2 times yesterday, he said her heart is fine and she had no temp, he also x-rayed her and said she has no objects in her stomach. He give her cepalexin to take and she throwed it up, so when I had her in last night he gave her a shot of batryl? Is there anyone that can tell me what to do or maybe a test that I could suggest to the vet. I need help!!!