Windows 10: Have I been hacked?! (User already logged in)

So i have a fairly fresh install of Windows 10 - i installed about a month ago. I keep my computer logged in and running 24/7.
I have a small network with an old domain controller running Windows Server 2000 (yes thats correct).
Every morning I unlock my windows 10 PC to start using it. This morning however, when i tried to unlock it, it said that there was another user already logged in! And it was the Administrator account, which I never use. And if i remember right it was the domain Administrator, not the local Administrator. So i freaked out and told it to go ahead and log that user out and log me in (as my usual user).
I'm kind of freaking out here because this sounds like bad news and maybe i was hacked.
Another strange thing is that i have a Windows 8.1 virtual machine running on this same PC, and when i tried unlocking it, the same thing happened - it said there was another user already logged in, and it wad the Administrator account.
Was I hacked? Im freaking out a bit here.
I dont use an email client, just gmail and i havent clicked on anything weird lately. The built in Windows 10 antivirus and firewall are enabled and running. This just doesnt make sense.
Any tips, hints, info would be great if you've got them.
Thank you!

:)

 

Current active users that are friends

The other reason I suggested this is that users can add characters to their username that are not alphanumeric (e.g. user*). This confuses things somewhat when looking at the list.

 

hacked? - computer logged into user name I never use


I got home today and woke my laptop from hibernation and discovered it was logged into the Admin account, which I never use. I am the only one with overt access to my computer.
I use a secured wifi, windows firewall (which may be my mistake), and AVG.
It seems I may have been hacked.
Any suggestions on discovering what may have happened and, if I was hacked, what I can do to protect myself?
Thanks in advance.

 

When a user logs in, other users are also logged in

Thank you for updating us. it is truly possible that another user is still being recognized by your operating system. To disconnect the other user logged in, you may follow the steps below:

• Press Windows key + Shift key + Esc
  to go to Task Manager.
• Go to the Users tab.
• If you see the other user there, right-click on it and press Disconnect.

Let us know how that turned out for you.