Welcome to the forums. I hope you make many new friends and that you have a great time here learning biblical truths for your life.
Were you born a boy and now you like to pretend your a girl? Or vise versa? Is that being true to who you are? No. Now, I have heard many people say that appearing to be the opposite sex feels like being true to one's self, but that simply is not really true. You are who you are and not who you aren't. If I am white, but pretend to be black, I am still white.
Outward appearances don't change who you are on the inside. If God made you a boy, then He wants you to be a boy. If He made you a girl, then He wants you to be a girl. God does not make mistakes, He made you the way you are for a specific purpose.
Sometimes we feel like doing things in ways other than they ought to be done, but we simply cannot act out on every one of our feelings. If we did, we all would be the biggest group of thieves, murderers, tyrants, adulterers, fornicators, liars, malice minded, mean, coniving, deceitful, conspiring, lazy, slothful, gluttonous, rotten people ever. So, we know that cannot act out on every feeling we come across. Many feelings we must put away because they are wrong and have no place in anyone's life, let alone the life of a Christian.
Also, to appear to be a girl if you are a boy (or vise versa) would be to bear false witness. We are commanded against doing that. What if you were a boy who alwayse dressed up like a girl and another boy "fell in love" with who he THOUGHT you were. Say you two decided to "stay pure" until marriage. Then, on the night of the wedding he finds out you are not who you claimed to be. You have caused another individual alot of hurt and wasted time, evergy and investment in a lie of a relationship. If you would respond to that scenario with "well, I wwould just tell him before hand who I was..." I would simply ask you this, "If you have to tell people who you really are, why not live who you really are in the first place?" Lying is not good for anyone, and we are commanded against it by God.
Another thing to consider is an outright command by God concerning deceptive dressing. It is found in Deuteronomy:
Deuteronomy 22:5 "A woman shall not wear a man's garment, nor shall a man put on a woman's cloak, for whoever does these things is an abomination to the LORD your God."
So, besides you being unable to change inside who you really are or the fact that it would be lying to live as someone you are not, there is a command that says it is unacceptable to God.
I hope this answer helps you find who you really are and the person God wants you to be instead of the lie that this world has sold you.
God bless you as you seek the Him.
In Christ, GB