How to login with Windows Authentication mode after domain name changes in SQL Server?
You should login with SQL authentication (with your sa account)
and run this query:

DROP LOGIN [OldDomain\UserName]
GO

CREATE LOGIN [NewDomain\UserName] FROM WINDOWS WITH DEFAULT_DATABASE=[master], DEFAULT_LANGUAGE=[us_english]
GO

ALTER SERVER ROLE [sysadmin] ADD MEMBER [NewDomain\UserName]
GO


You will then be able to login with your new domain name (be sure you change the domain name and username in the code).

If you need to recover your sa password you can read this article 
http://v-consult.be/2011/05/26/recover-sa-password-microsoft-sql-server-2008-r2/