@VioletLeaf I'm so sorry.
I can relate a little. My son (also autistic) wanted to be a girl when he was in year 1. Wanted to wear a girls uniform to school (cried about it). I was deceived at the time thinking I could support him through it, I talked to my therapist about it (pnd). I allowed him to wear girls pj's. Yet something did not sit right with me. I knew 'society' was now supportive of this but I did not feel it was 'right' in my own mind. In the end, I sat him down and explained how the girl he liked in class would not be interested in him as a 'girl' and if he was a girl, then he wouldn't get to kiss a girl when he got older as they would want a boy to kiss and not a boy pretending to be a girl.
That thankfully sorted the whole thing out and he gradually quit wanting to be a girl.
He still is very fascinated with makeup etc but I'm quite firm with him now, saying that make up is for girls only.
I know this situation is different from yours. And I know how heavy this can weigh on your heart as you love your child. Yet, you can be loving and supportive whilst telling your child they are 100% perfect the way God made them. By supporting their fixation to trans is subtlety confirming to a child that there's something wrong with them.
There are pluses to your situation, in that your child is open and honest with you. When I was younger, I got strange thoughts and feelings that I wanted to be a man but I never had the courage to tell anyone. I know now, that it was a phase or an OCD fixation for me.
The media is pushing this agenda and the poor children have no idea that they are being played.