I was playing all day yesterday when patch 4.0.3a came out, but this morning after i woke up i logged in and it is asking for an authenticator code after i type in my password. I changed my password and after i changed my password, i got a email from blizzard saying "We received a report that this account has been compromised, and we are taking the appropriate steps to help restore your access to this account as quickly as possible." followed by the link to battlenet. Now i am wondering if anyone else is having this problem or if my account has just been hacked. I want to know if this is something to do with the patch or if i have just been hacked.

I HAVE NOT USED ANY ILLEGAL PAYED SERVICES!