Follow that link from the customer support section.
Check that link for the answers you may need for now. I'll move your thread over to Customer Service, though, as they might be able to help you better. =) Hang in there, things like this are fixable.
First and foremost, you should be concerned with both account and computer security. Do a sweep with a virus and/or malware scanner (both would be best, but don't run them at the same time). Once you are certain you have found the source of your compromise or you have access to a known secure computer, you'll want to report your account to our staff using our web form:
This should also reset your password. While you wait for a response, anything else you can do to secure your account would be wise. Ordering an authenticator is recommended, as is changing the password to your e-mail address and Battle.net account and possibly setting up a new e-mail address to use exclusively with your Battle.net account. We have a lot of various security tips and tricks you might want to consider. Check out the links below - they'll get you started on the path to stronger account security. >^.^<