Don't worry, I had absolutely no idea what I wanted to do until the last couple of months of school. You can kind of make it up as you go along, I think everyone does :D
Getting older may seem scary now, but trust me it's kind of awesome! You get to experience so many firsts, I already feel like a different person to who I was when I first moved here.
Thank you!! and good luck for your last few years of school :)