BF was trans just like you, he knew how it felt to be misunderstood but wanted to support you just as much on your own journey. He had already started to transition himself and didn't mind giving you advice at all.

"Hey dude! I get it, you're feeling low, but don't let anyone ever tell you who you are. You know yourself more than others, and one day I promise you'll be just as awesome as me! Maybe even cooler."