Hi there Max,
I too am of the same age, and I too am fascinated with math. :)
Now that I think about it, I was inspired by two teachers and two books.
- The first book was a pretty old one called "Elementary Mathematics" by three Russian authors called G.Dorofeev,Potapov and Rozov. These books were published by a publishing company called Mir Publishers. They used to print extremely good books which were available for a pittance a couple of decades back, but they have shut down now after the collapse of the Soviet Union.
- The second one was an Indian book called "Challenges and Thrills of Pre-College mathematics". You might be able to order that if you try hard enough.
Another one I recommend is "Men of Mathematics" by E.T.Bell. This is a well-known classic, and I'm reading it now.
All the best for your future and I hope we meet someday in the math world! :)