my acc is being used by someone other than me, help

Ok, so i recently got the mission crates, the next morning ( today ) i woke up and i noticed that my "mp5" was used, when i dident even use it........

so i was thinking ???? wttf could have happend ?

then i think, "HAACK" so i dont know who the other player is ...

he/she changed my email address and as well as the security question .....

So GM's, please help me......