While I don't work in sound design specifically, I think I have some pointers that may help you.
I'm not sure how old you are (junior- 13?) but it seems like you know what you want to do which is definitely a good start. At that age, while I was consistently experimenting in audio production and DJing, I had no idea I could do it for a living, so I ended up in motor-mechanic college which didn't end well. So it's good you're focused at a young age. Just look into your chosen field and be 100% sure you have enough passion for it to keep you going. Be sure there isn't another subject you are equally passionate about which is easier to get into.
The next steps for you, I would suggest, is to get good grades in school, do best in maths and science. I've found that learning the theory of sound extends to other sciences, so the reverse is also true. But in the meantime, try to contact people in your school or community who work in production and ask them questions and get some real-world knowledge. Making connections is important. Don't be afraid to let people know what you want to learn about. Trust me, you can get away with asking anybody anything when you're that age, so take advantage of it!
While online forums are a good source of general information, some can be wrong in the information they give. Experiment for yourself, save up for, or borrow equipment to get some personal experience. Reading books on the subject is a good thing to do too, they tend to be more accurate than online stuff, and maybe subscribe to a magazine like Sound On Sound. At my uni, we always had SOS magazines lying around, amongst others. Maybe start with a more basic book on sound recording and the technology that is used if the aforementioned are too in-depth for you at the moment.
If you can, find a sound design-related university course or something. I can't suggest any for you but look into them to be sure you get the qualifications you need. The stuff you learn there will help you for the rest of your life. This will also give you some of the experience you'll need (and also a portfolio!). Studying music tech at university was the best thing I ever did. It gives you confidence in your knowledge and also, contacts, people with the same goals as you.
I'm sorry to say but luck seems to be a big factor in how well you do in these types of industries, but some would say you make your own luck! Good luck!