Fb

I just got a fb message from exN.... He isn't my friend on fb... How do I stop him being able to message me? Plus he liked a post I put on one of my friends pages so I got the notification. I didn't realize he could see what I post on our mutual friends pages.... How do I stop this? Is it rude to ask my friends to delete him too?

I feel violated. Wish he'd piss off and leave me alone (sorry about the language) it causes me instant anxiety :(