I'm 43 now and still don't know what I want to be when I grow up.
I started out wanting to be in the Navy, never made it, then went into a number of jobs doing various things and finally I've ended up in IT because I love messing with technology.
Don't sweat about what you want to be in life, just find something in life that you enjoy and want to do for a while and do it. If it doesn't work out don't worry cos if you are smart enough to get into college then you should be smart enough to do pretty much anything you want and you'll know when to change tracks and do something else.