No, you were not a dependent for Head of Household purposes and you are never a dependent when you file Married Filing Jointly.
Since you are legally divorced as of Dec 31st 216( that's when your filing status is determined), you may file as Single or Head of Household if you otherwise qualify. And your ex-wife, even if you claim her as your dependent - now that you are single and if you qualify to claim her - does not qualify you for Head
Of Household. You must have a qualifying
child, parent or relative as a dependent. A non-relative does not
qualify.
