You must secure your account. To do so, report that your Facebook account is hacked using this link.
Click My Account Is Compromised and search for your account by entering your email address, phone number or Facebook username.
In the list of accounts that match with your search, click This Is My Account next to your account. Then enter your credentials to access your account. You can use your current or old password.
Once you've accessed your account, Facebook will ask you to change your password and review recent login activity.