In texas law is a 18 year old having with a 15 year old considered statutory ?

my birthday is on august 15 1992....and her birthday is on septem 18 1995 i understand that is over 3 years ..and actually 3 years and one month ..soo doesnt that mean i lose the affirmative defense to prosecution clause?..is this illgeal?...i mean it says if under 3 years soo i guessing since its over 3 years its illegal?