Trying to stay strong

I need someone to talk to. I am 17 years old and throughout my whole life I've always felt like the ugly duckling in my family, I always feel like the black sheep that no one wants. I have no space in my house to just be alone. When I want to be alone it's either in the basement or in the bathroom. I hate crying infront of people and showing my feelings so my family probably doesn't know how they make me feel. My couins and younger siblings always make me feel like shit. They always make me feel insecure. I've always struggle with loving myself and just when I'm finally started to accept and love myself something has to happen. Either they joke about my insecurities they call me ugly and fat. I don't think I'm an ugly girl but I always compare myself to my cousins and I start to feel like they are right , i am the ugly one. I hate when people think that being a big girl is a bad thing. That being fat has to be a word used to offend someone. I'm always the one to be there for everyone but when it comes to me NO ONE is there for me. I don't know what to do anymore.