There's nothing wrong with eating in the library! That's what I did during my darker days in high school and now my old librarian is one of my best friends! Even though I've graduated, I still visit her and keep in touch! (PLUS you get access to BWW, which is fabulous.)
As for why you can't hold onto friends - it's not you, it's them. Trust me. (I've never been a believer in the whole, "If it seems like everyone else has the problem, it's you." idea.) You're probably more mature than most other people your age, and you've got different interests. But if you're not a biter and you don't smell badly, I don't see any other reason than that. (And since this is an anonymous message board and you don't know where VAncouver is, you know I'd be brutally honest/mean to you if I thought differently.)
"It's not always about you!!!" (But if you think I'm referring to you anyway, then I probably am.)
"Good luck returning my ass!" - Wilhemina Slater
"This is my breakfast, lunch and f***ing dinner right here. I'm not even f***in' joking." - Colin Farrell