The Reference Desk/Doctor 9 not telling Rose about his origins

1. In The End of the World, why did the 9th Doctor refuse to tell Rose Tyler who he is and where he's from?

2. Why did Rose wanted to know who the Doctor is and where he's from?

3. When Rose demanded the Doctor to tell her where he's from and who he is, he said "This is who I am, right here, right now, all right? All that counts is here and now, and this is me!" What did he mean by that?

4. Rose said "Yeah, and I'm here too because you brought me here, so just tell me!" What did she mean by that?

5. When he took her home on Earth in 2005 after she saw the planet burn up and there was nothing but rocks and dust in 5 Billion, why did he finally told her about the Time War, the death of his people, his planet burned and that he is the last of his species?