is this normal for a 15 year old?!

Yes, it is normal. No, you are not too young for this, it is very common.

I got my first pair of glasses before I started junior high school. Actually, I should have had them years earlier. I just assumed that no one could see the board at school. I did not even have a clue that I was one of the only ones who could not see it clearly.

Had a camp councilor not stumbled across the problem, I would have simply not been able to see things that others did. With the glasses, my eyesight was better than the 20/20 that some people mistakenly consider "perfect."

Expect your eyes to get slightly worse every year until you get to your middle ages, when it often starts getting better. Not a big deal, don't worry.

Personal experience plus research.

No, not at all. I had both in my eyes, until I had Lasik Surgery seven years ago!