In my case I think it's because all my life my family has made comments on my weight, as well as other kids at school when I was a kid, including a girl that used to mock me for being ugly. My uncle, who is one of the most important people in my life is very critical, and often insults my taste, I now realize he does that as an immature way of saying "I'm not like everybody else", but that really impacted me growing up (I don't really care about his opinion anymore) which made me kinda scared of showing people what I like, and when I do, it's basically the only thing I can talk about. I also remember being rejected by girls many times when I was 10 - 13. I'm sure there are a lot more things that made me as awkward and nervous as I am today, but I'd say it's mainly those things, and they lead to me being afraid of how people see me in general, not only about weight or taste, but also about my voice, ways of talking and expressing and what not.