I am over 18. I hope this information will be helpful. Dr. Spack gives a somewhat technical talk about advances in helping trans youth. There is also a shorter TED talk, but this one is the meat-and-potatoes. Some TRIGGER WARNINGS when he discusses some of us older transitioners who did not benefit from early medical treatment and intervention. But don't worry. It turned out fine for many of us, thank you.
https://www.youtube.com/watch?v=0tqil7Audws
This was such an amazing talk, it had me in tears when it addressed the suicide and self harm statistics going from horrible, to zero.