Why Does My Voice Sound Hoarse Ive Been Having This

Why does my voice sound hoarse ive been having this for 5 months and i asked my school nurse what was the problem and she said its part of puberty, but i just donr believe her. Most of the kids have a clear nice voice while i dont. Its so annoying because my friends and even teachers cant even understand what im saying! So i searched what was the problem and it said something about hoarse, then i searched what a hoarse person sounds like. And thats exactly how i sound! But i dont feel ANY pain. But whats weird its that it changes to a clear tone when i talk to certain people or when im at a certain place. Weird huh? Please help me i need my voice back.