If, after your Facebook account was hacked and the password changed, check your email inbox to see if Facebook has sent you a message about a possible password change. If this is the case, you can change your password again via a link found in this mail.
You may no longer have access to your email address. Maybe you have only forgotten the password, maybe your email account has been hacked. In either case, you can use the “Forgot your password?” button on Facebook’s login page. Follow the instructions. Provided that you have stored “trusted contacts” when creating your account, Facebook offers you the possibility to send these friends a security code. With this, you can access your account and change the email address stored there.
If all of the methods listed here fail, contact Facebook directly. Facebook will help you gain access to your compromised account with a dedicated page.