Am I fat for my age?

im 16 , (sorry if I have bad English I'm from israel) anyway, I'm 1.63 meters, I'm weight 55 kg.

people that are in my family say I'm thin , I'm not fat and surely don't have a big ass, but its family they always say I'm beutiful no matter what so I don't always belive it.

so there is always this friend I hang out with a lot at school, she is always telling me I have a big ass and I'm fat and huge and everything, that makes me really want to lose weight, I've never thought I was fat until she started telling me I was, I always thought I had a really beautiful body, I also never mention or ask anyone if they think I'm fat because I will feel like an attention whore, so I came here to ask this.she also always tells me that people talk behind my back and tell how big my ass is and how fat I am, its really making me feel bad. I always try to put small and tight pants so it will make my ass look smaller maybe?

i don't know, but anyways I don't what to do, how can I make myself feel better, anything..

Am I fat for my age?
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