I came to US with F1 visa from 2008 to 2012 and went back my original country. I cam back for Graduate School study in 2018. Was I tax resident for 2018 and 2019?

[achilo123]

I entered in July 2008 with F1 visa and left in October 2012. So if I was considered tax resident alien for tax year 2018, but I filed my tax return as non-resident alien, what should I do this year to amend that? Thanks.