That's so bad! I don't know if I'm late for this question, but I have some good tips!
First of all, you need to confirm the hack and report it to Facebook. Then, change the password (if it's not too late) and log out from all the accounts you're working with. Once you've done this, you can check your permissions and improve your authentication system since Facebook offers more resources to strengthen this process.
I don't know if your hack will allow you to get to this point, but it did work for me when I was in your situation.
I've been working from home with several Facebook accounts simultaneously, and this happened to me A LOT. It's so frustrating!! Accounts and users' information gets mixed up, and Facebook recognizes it as some error. Well, working from home has lots of advantages, but when these things happen on your computer, it's not that great.
I hope some of this works for you!
