Someone please help…My Facebook has been hacked?

My friends have been getting video links on their wall, that i never sent and also video link are on my wall that i never posted! I am going to download an antivirues software, thinking that might help, but if anyone has gone through this and know how to fix it please tell me. I have changed my password and that didn’t help and i don’t want to create a whole new account so i need Help!?!

just change your password ..
surely you have entered it on other site or mobile application
change your security answer too
or contact facebook

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