Overall, it sounds like you should do it. Travel has a huge effect on your life and I am a big advocate for school leavers taking gap years. You might find teaching kids English difficult if you have no affinity for kids - remember that whilst you want to leave your comfort zone, you don't actually want to be doing something you dislike. I don't connect with kids and never have and so I just find other volunteering and travel experiences that work for me (like hands on farm work or helping building homes). That's my only reservation about your plan, to me. But the beauty of travelling is it's flexibility. If you don't like where you are or what you're doing, you can usually do something about it pretty easily.
You are very normal in feeling terrified. I think you are very brave doing something like that so young. You will grow and learn. Don't expect it to be easy at first. Even the most outgoing of people take time to form new relationships. It usually takes a good couple of weeks (or more) to feel like you're a bit at home. And if you've never been away from home before, even two weeks can feel like ages. But just push through that stage, I think.
Go for it buddy. Cram as much into life as you can. Good luck with your exciting year ahead x