What you have to do is change your password and the email address you use to access Facebook immediately. You can easily sign up for a new email at mail.yahoo.com or gmail.com.
If the person gained access to your account through a keylogger or trojan on your computer then you need to run a virus scan and remove those programs from your computer immediately.
Otherwise I don't know how anyone could hack your account unless your password was weak or you gave out your information to someone.
It takes 14 days without logging in to permanently delete an account on Facebook once you follow this link: https://ssl.facebook.com/help/contact.ph…