Going the digital way has too many risk factors with it. May be one of your friend got an idea about your password and he experiments that with your Facebook account. If he succeed, probably you won't be aware of it until he do some ugly job on the behalf of your identity. Here I am describing one more step to do, heading towards online security.
What is Facebook Login Notification?
Login Notifications are an opt-in security feature where alerts are sent to you each time your account is accessed from a new device. New devices means those devices which you have never used before to access Facebook.
How to turn on Login Notifications
1. Go to your Security Settings page (Account > Account Settings > Security)
2. Click on the Login Notifications section
3. Check the box next to the type of alerts you'd like to receive and save your changes
Now when you login to Facebook from any device or computer you will be asked to set a name for that device. You can set any device in Recognized Devices list. So you will not be asked for that particular device afterwards. It is strongly advised not to mark any public computer in your Recognized Devices list.
Actually cookies stored in your computer help Facebook to identify your computer. But if somehow you clear your browser cookies then your computer will not be identifiable and you would have to name your device again.
Each time when someone or you yourself log in to Facebook, an alert will be sent to you to your e-mail address as well as on your mobile.
If you ever receive a Login Notification from an unfamiliar device or location, don't be panic but reset your password immediately to secure your account.