Whether you are married or unmarried will depend upon state and federal law. Tax law says an individual legally separated from his or her spouse under a decree of divorce or a decree of separate maintenance shall not be considered as married.
Many couples are legally separated but are still considered married under state and federal law. If your divorce is not final, you are still married unless your state allows for a decree of separate maintenance. You will need to ask your attorney whether your current legal status meets the definition of a decree of separate maintenance.