Hackers may have accessed your account by changing your password or sending you unwanted emails. You can also verify your login details by visiting Facebook's "Where You're Logged In" section. These details may allow unauthorized users to log in again and see what you're doing. You can also change your password in order to prevent future logins. Once you've taken all of the steps needed to protect your account, tell your friends about the situation.

For more read - https://onlinegeeks.net/facebook-account-hacked-how-to-recover/