Why is facebook doing this to me?

[Cant]

when I logged into my account heres what it said
Dear My Name

We've detected some unusual activity on your Facebook account,
and it looks like your password may have become known to a third party.

In order to protect you and your Facebook account we need to confirm your identity and the authenticity of your account.
Please provide the following information so we can avoid it in future.

Then it started asking for my credit card details and I cant go on facebook but I can on my other computers and plus I never did anything wrong on facebook I add people that I know and stick to the rules