Do you have any dependent children?
You may file head of household if you maintain at least 50% of the household you and your dependent child live in. You are considered unmarried if you have not lived with your spouse for the last 6 months of the tax year.
You can find this information for verification on pages 7 and 8 of Pub. 501: http://www.irs.gov/pub/irs-pdf/p501.pdf.