This shouldn't have happened, since Facebook checks if the email is already used or not.
If you are not the account owner and are attempting to sign up for an account, then please be aware that you can only sign up for one Facebook account per email address.
However, try using this form to regain access to your account.
Or try one of the following procedures:
I can’t remember which email address I use to log in to Facebook.
- If you registered a username, try logging in using your username and password. A username is your personalized Facebook URL (web address) and appears in the location bar of your browser after "http://www.facebook.com/" when you view your profile. After logging in, visit the Account Settings page to locate the email address you use to log in.
- Try logging in using your mobile number and password. If you have confirmed a mobile number onto your account, you can log in with your mobile number and password. Be sure to add the country code and remove leading zeroes and symbols when you enter your mobile number.
- Try locating your account on the password reset page.
Tip: If you can’t find your account using one option, try using the other options to find your account.
- Ask one of your Facebook friends to view your profile and send you the email address listed on your account.
- To do this, ask your friend to click on the "Info" tab on your Profile page and scroll down to "Contact Information."
- Once you receive this information, try logging in with that email address.
- If you have followed the steps provided above and are still unable to access your account, click here.