Your marital status will be married because you were not legally separated or divorced on December 31st. 

However, your filing status seems to be Head of Household. If you qualify to file as head of household, your tax rate usually will be lower than the rates for single or married filing separately. You will also receive a higher standard deduction than if you file as single or married filing separately. 

You may be able to file as head of household if you meet all the following requirements.

1.      You are unmarried or considered unmarried on the last day of the year.

2.      You paid more than half the cost of keeping up a home for the year.

3.      A qualifying person lived with you in the home for more than half the year (except for temporary absences, such as school)

Considered unmarried means-

·You file a separate return.

·You paid more than half the cost of keeping up your home for the tax year.

·Your spouse didn't live in your home during the last 6 months of the tax year.

·Your home was the main home of your child, stepchild, or foster child for more than half the year.

·You must be able to claim an exemption for the child.