Unless Facebook is sending requests on my behalf, lately I haven't sent a request to anyone but one person. And I definitely know him. Do I have a virus? I have been spam accounts sending me friend requests so that might be it.
Most Helpful Guy
You could have been hacked, though It has done that to me before because I sent way too many requests before1
Most Helpful Girl
Luckily you've changed your password, you can also increase privacy settings so you need a code every time you login to a new browser, it can get a little tedious, but definitely worth it with the risk of being hacked.1