My Kitten Is Not Eating, What Should I Do?

We first put her on dry science diet kitten food. We've only had her about a week. We don't know how old she is but she was eating dry food at the pet store. Now, She is sleeping A LOT. And wont eat but two pieces of dry food and we tried canned Friskies or Fancy Feast, she wont eat either! She will only drink water and eat only the first centimeter of food. HELP!