How to hack back into your Facebook.?

One of my ex-boyfriends knew my Facebook password and they hacked into my Facebook to be a joke. well then they took advantage and started posting stuff that ain't true and people think it's me. now hes gone to far and changed the password. he's really smart with the computer and he said if I make another one he will just hack it so now I need to know how to hack back into mine so I can change the password and block him forever. (I need something safe and I don't have to download if possible) thanks