How did you find out Santa isn't real?

I'm 13 and i had some doubts when i was 8 when i realized the NORAD Santa was animated. I was a little boy and was so confused and then christmas day i noticed santa used all kinds of different wrapping paper at my grandparent's house and the same paper at my dad's house. i had alot of doubts and kinda forced myself to believe. I've been writing letters every christmas season and watching and calling NORAD with my little siblings. I had doubts last year and read the letter "Yes Virginia" and believed for one more year but this year i sucked it up and accepted the truth:there is no Santa. I went on the phone crying to my dad that i found out and everyone i asked kept reinforcing the belief in me and he sent my grandma a text about what i had called him about and all my grandma said to me was "St Nick was a real person and i believe in Santa." But i know the truth.