Will people know if you're on their Facebook account?

[Sylentstep]

My friends said they found out my password and that they have been going on my Facebook account and reading my messages and doing other things. Nothing seems like it has been changed though. I know I can just change my password to prevent this, but is there a way that I can tell if somebody has been on my account? Like if I am on my phone and they log on from a computer will I be able to tell if they are on my account?
Yes you can access your account from 2 different places at once, i've done it to myself before.

[Danielle]

No because u can't access your account from 2 different places at once

[Insane_mad_maniak]

change your password, when someone trys to log in with your old password, if they do it a few times next time you log in you will be given a message that there was an attempt to log into your account which failed and to verify if it was you.

[me]

You could tell if they are on your account by you notifications and messages. If your messages have been read by someone other than you, you'll know because you didn't them; or if you get a notification and they open it before you that another way to find out. hope this helps