I'm shy - why do people dislike me and why would someone with 700 Facebook friends UNfriend me?

[Carbonation]

i am very shy - always have been, and sometimes people are nice to me because of it because they know i am shy, but other times, people just really don't seem to like me. and this is not one of those "shy person having low self esteem and lacking confidence in social situations" i am talking about some people that for some reason just don't like me. i keep to myself and i don't get in anyone's face, i mind my own business. i just don't understand why they don't like me.
i even remember growing up there were always nasty girls who hated me and would be very cruel. now i am 24 years old and occasionally encounter similar girls. i am a very calm, laidback person so i don't understand why anyone would get mad at me or not like me. i'm nice, i swear

and now i noticed that a teacher i had in improv class, who told me i was funny and seemed to like me when i was in class, has now defriended me on facebook! the guy has over 700 friends, so clearly he's not exclusive about who he has as a facebook friend. yet he went through his list and for some reason found having ME as a friend was a huge burden to him and he just couldn't have me as a facebook friend. i did NOTHING to him. i always thought he liked me, he says hello to me if i pass him. i don't GET it. i know it's not a big deal, but still, he made a conscious choice to remove me from his list of TONs of people. and i just noticed a guy at my work did the same thing. i recently hung out with him after work too! i always thought he was nice, but now i am not sure........
Please Please please BE HONEST
i am NOT overanalyzing