Am I permanently losing my voice?! Please help me!?

Okay. So, I sing A LOT. It's my life - I've been singing since I was 3. I've been told I have a great voice, and I really do not want to lose it. So, I was singing today, like usual, and all of a sudden, those big notes I can usually [attempt] hitting came out kind-of soft and raspy a little bit. It kind-of felt as if my voice was trying to avoid that note. It sounded like similar to what it normally was, but it was off. Well, I can sing fairly high in falsetto, and some of those notes are like that too. What I don't get, however, is how I can sing perfectly fine in higher notes and lower notes, but not that certain note. So I need to know if it's because maybe puberty, since I'm 15, or maybe because about a month and a half ago I had bronchitis and an upper respiratory infection, or maybe because my brother and I were wrestling, and he choked me a little too hard. Those have all crossed my mind - I really and scared that I've permanently lost a part of my voice. So do you guys think I am? And what can I do to possibly save it?