Can't help you out much because I don't know you - and you're probably still figuring yourself out (if you're like me this will go on for a while)!
However, I do feel for you and can share my own experiences from that point in life.
Through junior year I didn't know for sure what to study in college. Worse, I was starting to stress about career choices - having a nasty form of agoraphobia that prevents any kind of travel, all kinds of great careers and jobs were not an option. I was strong in math, and liked it, so I considered studying that in college, or the sciences that are math-heavy (e.g. physics). However, I was worried about the somewhat limited career prospects after graduation - going the route of academia is always an option, but I didn't want to be limited to that.
Late junior year, a certain physics project sparked off an interest in simple electronic circuits. Spent the summer teaching myself about them; learned very little - turns out I'm not so good at that stuff, heh. However, at that point I planned to enter GA Tech as an Electrical Engineering major and figured strong math skills would carry me through.
Senior year, I signed up for the AP Comupter Science class. Not sure why exactly; suppose I figured solid computer skills would help with EE, plus everyone older than me was advising "ooh, are you into computers? you SHOULD be!" (this was just a few years before the dot-com bubble). The class was taught using Turbo Pascal (a "cute" programming language for students), and I LOVED IT right from the start. I dug that I could get what I liked about circuit design - conceiving, designing, and build your own tools/applications. Additionally, programming seemed far more expressive and came more naturally (I suppose from the background in math/logic), and was less tedious (good debugging tools, instant feedback, no need to source parts, etc). I also dug that it felt relatively easy, while other peers struggled. So I switched my declared major from EE to CompSci before entering Tech, went through the program, picked up a job (despite the recent dot-com bubble burst), and have been working (mostly) happily for 10 years :)
For senior year, I'd say stack up on those AP/college-level courses - take courses at a community college if your school doesn't have good AP courses - and just see if anything resonates with you. Experiment; those level of courses are the only ones in a high school that have any CHANCE of teaching slightly interesting stuff. Of course there's always the various trades, which can lead to a great career, but that's not what academic institutions are really for (some would say software development is really a trade).
Edited by mulveling - 4/24/11 at 1:00pm