You have to file as Married filing jointly or Married filing separately, for 2017 because your divorce was not finalized in 2017. According to page 6 of pub 501 under the headings, "marital status" and "considered married", "in general, your filing status depends on whether you are considered unmarried or married". It goes on to say, "you are considered married for the whole year if, on the last day of your tax year, you and your spouse meet any one of the following tests. #4. you are separated under an interlocutory (not final) decree of divorce." https://www.irs.gov/pub/irs-pdf/p501.pdf
Your filing status options for 2017 are married filing jointly, married filing separately; and head of household. If you meet the requirements to file as head of household.
Please refer to the following FAQ to review the requirements for head of household.
: https://ttlc.intuit.com/replies/3288637