Try to reset your password at My Apple ID (appleid.apple.com) as described in this document:
iCloud: Find My iPhone Activation Lock in iOS 7
http://support.apple.com/kb/HT5818
If you forget your password, you can reset it at My Apple ID (appleid.apple.com) or by contacting Apple Support and verifying your identity. Once your password has been reset, it will work normally with Find My iPhone and Activation Lock.
If you forget your password and cannot reset it, you will lose access to your Apple ID and may be unable to use or reactivate your device. To help prevent this, visit My Apple ID periodically to review and update your account information.