Everyone goes through that part in life where they have absolutely no idea what they want to do. To be completely honest with you, don't sweat it. You're only 15, you're still in highschool. You have time to figure out what you want, it'll come. And don't be afraid if you start going to college for something and you want to switch majors. I started off in college as an english major, halfway through I switched to graphic art and design.. and now I'm pulling out of college and going for cooking and pastry at some college 700 miles away. I'm not saying that will happen to you, I'm just saying don't be afraid for it to happen. You have to try things to figure out if you like them or not. You'll never ever know until you try.
So my advice, sit back, enjoy your ride through highschool, and quit worrying. Do whatever feels natural. And if you end up not liking what you're going for, switch.
"If you're doing something you love, you'll never work a day in your life"
And it's so true.