Problems with activation code.

I bought Battlefield 3 for PS3 about a year ago and I've been playing it just fine, without having any  issues related to bugs or account complications at all. But last month my 12 year old brother messed up with my videogame, and now it is asking for my activation code again, which won't work. I always end up getting a "the code you entered may not be correct or may be no longer valid" message, and then I'm unable to play. Could someone help me out? Did I lose anything in my account? I'm willing to send pictures, if necessary.

Thanks.