I just realised you can't sleep in hostels if you're under 18 years old. Is this the same for staying at a campsite in Italy? I really need help because I already planned a whole vacation around camping.
I think you're going to have problems with camping.
The age of responsibility in Italian law is 18 years.
I've looked at the terms and conditions of a number of campsites, and they all say that each group must have at least one responsible adult.
I suspect that this will vary from site to site depending on their insurance etc, but on a quick search I was unable to find a site that would accept you.
And you can't bluff it, as they will ask to see your passport when you arrive.
But it wasn't hard to find hostels who will take you, provided you have original written permission from your parents. Obviously, it would be sensible to contact them in advance to make sure there is no misunderstanding, so you don't have problems when you arrive.