If you have filed all your taxes since you arrived in 2012...you should be OK to apply now.
2012 taxes filed in 2013, 2013 taxes filed in 2014, 2014 taxes filed in 2015 and 2015 taxes filed in 2016: that is 4 years as needed.
Except u didn't file 2012 taxes that you were supposed to in 2013...