99% of the time this is because you have accidentally made two accounts. Find the email receipt for your order and that will tell you which email address you originally used to sign up.
If you can’t locate your receipt but know you have been charged, email firstname.lastname@example.org. Please provide your full name and the Transaction ID on your statement if possible.
Likewise, if you have signed in with Facebook and your account is empty then this most likely means you originally joined with your email address. Sign in with your email address and then go to Settings to link Facebook for future sign-ins.