Need help with how to file.

The past 2 almost 3 years I've been separated from my husband not one of us have not filed for divorce yet I haven't due to trauma and deaths in my family . I have a no contact order on him for abuse of the children. Last year and the year before we filed married filing joint because I did not know what to do he sent his info to the tax preparer and it was done that way due to no contact. I have solely paid for and provided a home for the children and I have paid all the expenses except for the electric bill was his only child support. I have paid for everything els and the kids are in my custody. We have lived separate and I do not want to file my taxes with him I plan on filing for divorce within the next month. My question is do I qualify to file alone as Head of Household or do I have to File Married separately and what are the differences between the two? Please Help.