Thanks @Empireapple – your last paragraph is nearly identical to what my parents told me, actually, and now my sister thinks this is a sign I’ll find my true love at college or something 
@tucsonmom I hadn’t considered it from that angle yet about jobs, but you’re right. I didn’t realize until now how much of a strain it would have put on my family if I attended another school; I would have had about twice the debt I was expecting and this way, my parents can use the money for my sister and we can both graduate debt-free, so I’m grateful. In a way, getting rejected was a good thing because it made a necessary decision very easy (whereas it would’ve been hard to turn another school down).
@badgolfer, I can’t disagree with you entirely because yes, I could have done much more, and no, my applications were not absolutely spectacular. Part of that was because I was naive about what I needed to do; part of that was because, as @PurpleTitan stated, I didn’t think it was “worth” doing things I wasn’t interested in for the sole purpose of college applications (and even if I had, it’s very possible I’d be in the exact same spot and feeling even worse). But it’s not as though I did nothing in HS (I worked over 40 hrs/week this summer), and I did work very hard on my essays – I just know that, despite being my personal best, they weren’t THE best.
I’m also beginning to think that “you must major in STEM and go to grad school” is the new “you must go to Harvard” for top students, so I’m still unsure about that. But yes, you make a very valid point and it’s something I will seriously consider during my time in college, as I’d rather be prepared and not need it than vice versa (and I’ll need a job eventually, regardless).