Is it normal to shave or trim my public hair. no one will see it, but is it normal for most teens my age to?

Yes: Many teens do this. There is no medical reason to do this, if you choose to do this it should be for personal reasons, not to give in to peer pressure.

Yup: Teenagers of this era love to modify their bodies any way they can, including shaving or waxing their hair wherever it may grow. I don't consider this an issue worth fretting about. Just be sure the teenager is clean about what they do to avoid infection..