If you do addition and subtraction literally any way other than the way you were taught in school and you still get the correct answer, I need you to stop saying you are bad at math.
If you can manipulate numbers to make a system that works for you and you get the right answer you are not bad at math. You are very good.
Kids need to know that adults do simple arithmetic many different ways and it's okay to have a favorite even if it is different than the norm.
You are good at math.