Does it count as a duplicate file if I filed my 2017 and 2018 recently and now I am trying to e-file my 2019? I am just trying to e-file my 2019 tax return.

If you mailed your 2017 and 2018 paper returns recently and now you want to e-file  your 2019 you should chose the option that you did not file 2018 because IRS probably haven't process 2017 nor 2018 returns that will let you transmit your return with no problem.  If I understood correctly your question then I can say that by filing your 2017 and 2018 returns will not affect your 2019 there is no duplication.