How did someone hack my facebook account?

[b]

actually someone tried to. so a bit of histpry, please bear with me

about a year ago I became paranoid about facebook so I deleted all of my photos, all info is hidden, most of the groups and apps have been deleted. and I rarely post anything. the email I use for facebook is strictly for facebook only and i don't use it otherwise. the same goes for the password. I haven't accesed it from a computer in a while, I only acces it through my phone. i also activated login approvals via mobile phone.
so a few days ago I got a text with the facebook security code while I was nowhere near a computer.
I checked and I had a notificaton that someone tried to acces my facebook from brooklyn with my email and password. (I am in Europe).

How is that possible? What did I do to compromise my account?
@ Abhishek: as I stated, I don't ever use that email address and as for my phone number it isn't publicly listed.

@ Isabella: as I already wrote, I have deleted all apps a year ago and didn't add any in the last year. and I never click on any links.