How do I call myself using Facetime?
The short answer - you can either call a phone number (iPhone + FaceTime) or an AppleID (iPod/Mac/iPad + FaceTime) and you can't call another device with the same number.

To call back to your mac (or any other AppleID device) - you'll have to make a second account with a different Apple ID. Similarly - there's no easy way to get the phone number into another device since that gets authenticated over SMS in the background and not user/password for AppleID.

If you are calling from an iPhone - you can call your AppleID devices (they all ring and any one can pick up), but for AppleID based calls - you need to call a different AppleID unless Apple ever changes the current software.

Last clarification - AppleID is just a string but most people use an email address since that is more likely to be unique to one person.