My Shihtzu is about 2 yrs old and has never acted this way. She has thrown up maybe three times within the last week. She has energy afterward and continues to eat. Although this morning she now has diahrea and she now doesn't care to eat or drink water. As she lays on the floor her stomach seems to sqeeze itself in and out every now and then like she is going to throw up again... what is it?

Often these things will clear up in a few days, but it sounds like it is time to call the vet now.

I agree with labman. Since this has been going on for a week and now she is off her food, water, and has diarrhea, she can dehydrate quickly. So, it is time for a vet check. It could be anything. She might have eaten something she shouldn't have when you weren't watching. Please call your vet and get her in for an examination. I hope it is something easily diagnosed and resolved quickly. Good luck!