I need to know what this means?

My boyfriend and I have been arguing alot recently and I think he's talking to someone else on Facebook!

This "active now" or "last active 5 minutes ago" is really starting to annoy me!

His chat is turned on. So when he's on chat the green dot will appear. But then that will go so I think he's offline. But when I go to 'messages' and go onto his inbox, at the top will say "active now" or "active __ minutes ago". But when it says he's active now, there's no green dot so he's not on chat.

He has an iPhone and his Facebook is signed in all the time. So what does this active now or however many minutes ago mean?
Does it mean he's on Facebook but his chat is off and he's talking to someone through messages? What's it mean? I've asked is he talking to someone else and he said he isn't.
It's really starting to annoy me!

It means when you get on your fb and when you get off.sometimes it will say he is online but he isn't cause fb is just stupid like that. If you would liike to tell me more details and stuff i would be glad to give you some more advice just email me at damyon.mincey@gmail.com