With 500 million users on Facebook, there may be a few people stalking you. So what can you do about it? Simple, just block them from Facebook so to them, you don’t exist.
To do this, visit https://www.facebook.com/settings?tab=blocking, and under Block Users, start entering the name of the person you wish to block.
Once you block someone, they will not be able to communicate with you, or see you on Facebook. It would be like you are not even on Facebook to them.
A word of caution, they may still be able to see public information about you when they are logged out of Facebook.
If you have mutual friends, they might communicate with other people who are on your friends list to see what you are up to.