Character forced to different server?

So I decided to start WoW again after a few months, only to find my character, Gilas, missing from Chromaggus and now on the Illidan server, now named Gillascc. What happened? Did Blizzard do this? Or was this the work of a hacker (a few weeks ago I got some email saying my password changed..? I changed it again). AND I cant access him, it says character update process I recently initiated needs to be completed..whats that?

Help? Thanks.