Possible hacked account

I got a notification the other day saying this guy accepted my friend request, however I know for a fact I did not send this person a request, I don't even know them. The profile looked fake with only one picture, no information or many friends. No one else knows my password which I change regularly, I only ever use my laptop or phone for Facebook. The weird thing though, was that soon after I got the notification this so called person uploaded many pictures of my ex boyfriend, who I haven't spoken to or seen in 4 years nor do I ever want to. I deleted him straight away of course. I'm just wondering how this happened, if someone's having a joke or if my account was somehow hacked because I DID NOT add this person.

much appreciated if anyone could shed some light on the situation.