If you were to do a confidential survey of your classmates, I bet a large percentage would be feeling exactly the same way you do. "What am I doing here? I don't belong here. I don't fit in."
This is quite common at top schools in particular because everyone they admit is used to being successful in high school, and now they are at a place where most of them are average (because everyone around them is smart too).
I'd advise you to stick with it. Many freshmen overload themselves, trying to do and join too many things, so back off a bit on your schedule, find one good social group to belong to (not five), and consider making the library your main hangout. Sit in the main reference area for a couple of weeks and pretty soon you'll be recognizing people, they'll recognize you, and you'll have some new academic friends and supporters.
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There Are Four Lights!