Hackers are changing my password

So long story short, I got into this dispute with a guy. He said that he was going to "lock my account" and that I wouldn't be able to log on. So now, just then, I logged off and my password.. it has been changed, although I received no notification that my password has changed. Whenever I do try to change my password, it says I have excceeded the daily limit. I have no idea what to do now? Advice please? As odd as this sounds, but this is actually true, and you may find it hard to believe. So I need your advice.. is there anything I can do? I am logged in at the moment