As Mike9241 mentioned, your filing status for that year will have to change to single, unless you also had children of your own that might qualify you for Head of Household. You need to amend the return, and file a single return and remove the children from your return.
One thing you might want to try is to claim innocent spouse relief, since you filed a return with your spouse and you didn't know he was also married to someone else at the time.
For more information refer to the following TurboTax and IRS links:
What is an innocent spouse and how does it differ from an injured spouse?
I am sorry that you are going through this.
@smj5041
