Why Can't I Reach my High Vocal range!?

I'm a dude. !7 years old. I sing A day to remember. But everytime I sing Along and there comes a high Note I can go along with it But It's not LOUD. It's the same note but Low? Idk but one's I have to hold My voice will start to fade or crackle. I can't keep it there. The girls Get it like its NOTHING! How can I make it to where over Time I can get The Vocal highs as loud and as good as the singer gets them! any videos,warmups or anything? Thanks!