Im really unconcious about my body :\?

im a 14 year old girl, i weigh 54.3 kgs, and im 1metre and 68 cms. im kinda not happy with my weight, like i want to be skinny, like i see girls in bikinis at the beach and theyre all got perfect bodies and like mines ugly :\ i have like a smiliar body to marilyn monroe? like i have big thighs and well not a small but not a big one, and like my hip area is kinda wide ? :\ eww