What is considered fat... what is skinny.....AHHHH

I would consider myself skinny but I've been doing a lot of reading and it seems to me that maybe others would consider me fat, or maybe thick :( I'm only 5'1 and I weigh 120 pounds but I do have a bigger butt and I guess more muscular legs ... but I have a small waist so I don't know what to think about myself... is media conforming people to think that if you don't look like all the people on the magazines and TV shows than you are fat ... ugh.
What is considered fat... what is skinny.....AHHHH
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