Do you mean that you no longer have access to the email address registered on your account, or your account has been hacked and information changed?
For the first option, you can try using your other recovery methods to recover your account, such as your phone number. Follow these instructions for methods to recover your Facebook account. If everything fails, try recovering your old email address first, and then retry with Facebook.
For the second option, you should visit this page to secure your Facebook account immediately. Check also your email, Facebook may have sent you a message allowing you to reverse the change of your contact info.