So, multiple devices, multiple locations.
What if someone’s using your account whilst your out or sending messages as you from a legitimate login? So called ‘frape‘.
Now Facebook tells you where your account is active. Sort of.

Active Sessions:

Under Account Settings, Security Settings you’ll find one last option, Active Sessions.

Normally there won’t be many as most applications are nice and log you out of a session when you close it. But Browsers and web apps may keep the session alive to make your access simpler, so that you aren’t constantly logging in.
A little reminder of your current connection starts the list.
Then a reasonably informative list of current logged in sessions, including the “Authorised Device” name and a guess at the type of device. Oh, and a really, really approximate location.
To end any suspicious session, just click End Activity and whoosh – it’s gone without any further prompt.
Nice place to just keep an eye on how your account might be being accessed. The time last seen is a useful indicator for the paranoid.