I can file head of household. why is this not a option for me

I'm not sure why you don't qualify.  Please review the child's information under My Info or Personal Information.  Be sure that you check NO for the question " Did "My Child" pay for more than half of their living expenses and other support? (We know My Child's a kid, but we have to ask.)

These are the qualifications for Head of Household.

• Head of household is a filing status on tax returns used by unmarried taxpayers who support and house a qualifying person.
• To qualify for head of household (HOH) tax filing status, you must file a separate individual tax return, be considered unmarried, and have a qualifying child or dependent.
• The qualifying person must generally be either a child or parent of the HOH.
• The HOH must pay for more than one-half of the qualifying person’s support and housing costs.
• The purpose of the HOH filing status is to provide single or separated individuals with dependents a financial boost.