Hi Mal, welcome and yes this site is a life saver!
The first person I came out to politely reminded me that "God makes us perfect in the womb."
To which I replied, "Absolutely, God made me perfectly too! As the girl I am, in the boy body I was needed to be in for a good portion of my life. So that I could accomplish things that God planned for my life."
She was briefly stunned and then said, "I never really thought of it that way." Now I do not think I have convinced her of this, but at least I did get her to pause. I think more people need to hear this and I was glad to have since read it in a good book about transitioning. So I know I am not the only person who see's God as capable of doing this for a reason we may not even notice for ourselves.
I have since looked back and can see examples of things I have done in my male body that have served a strong and powerful purpose to others in my life. These things would not have come about had I not been a girl in a boys body (as simply being a boy in a boys body would have fallen short for these things.)
Mal, I am absolutely certain you were born perfectly, just as God had intended, just like your mother says. However, God has also worked in mysterious ways, they all admit to this too. Which is why I get perplexed by those who use this argument, yet do not see us as perfect as they themselves must be as hetrosexuals.