I want to deactivate Adobe Digital Editions on devices I no longer have so I can activate new devices.

I can not activiate new devices because I have hit the 6 device limit.  I no longer have 3 of the devices so I can not do it on the device.  When I have gone to my account, there is no list or any way to see what devices I have listed.  All I know is that I have hit my limit and can not make my new ereader work.  Is there anyway to do this without creating a new account with a different e-mail address?