Quoting ambermoe:" I honestly don't know how to tell my parents that I'm pregnant. I feel as if they are going to kill me ... [snip!] ... week today. I don't know what I am going to do. Or how I'm going to tell my parents. If anyone knows anything. Please speak up."
You can't be one week pregnant. I suggest getting a book like what to expect when you're expecting so you can learn the basics.
And just say it. I don't think there is a way to sugar coat a 15 year old being pregnant. Tell them sooner then later.