Am I resident alien or non-resident alien for tax purposes?

[Nishant]

I entered USA in August 2015 as a F1 student, and currently working on F1 OPT.

[LinaJ2018]

You are a nonresident. 

As an F-1 student, you are considered a nonresident for five years (2015-2019).  Starting from January 1, 2020, if you stay more than 183 days in the US, you will be a resident on your 2020 taxes.