Married filing Separate or Single?

I live in Georgia and have been separated since July 2019 (living together but living separate lives since way before then). Going through a rough divorce. I'm wondering how I should file - married filing separate or single/head of household? Despite being married and living together in 2019, I provided my own things and necessities that our kids needed. The IRS said that since we have been separated and already have divorce in motion, that I could claim both of our kids. I'm paying childcare and not receiving any type of monetary support from him at all, and I am also the legal primary custodial parent.