How can I lose weight?

I am only 13, but I want to lose weight. I honestly know that at my age I shouldn't be worrying about things like that, but I have anxiety and I'm supppeeerrr worried someone would judge me pretty badly if they saw my body. I feel pretty confident about other things, I have a boyfriend and he has made me feel so much better about myself since we started dating. I just can't get over my body. When it comes to my anxiety and meeting new people, I always worry about things like, "What if they don't like my hair? (I have really short hair) What if they don't like me? Or my personality?". When it comes to my anxiety, I think I am the most worried about summer, when I start going swimming again. I want my body to look alright when wearing a bathing suit, because of my anxiety. I even hate walking around in a bathing suit in front of my family. Even if people don't know me what so ever, I still hate walking in front of them. I just want to be confident with my body, and that's it. I want to be able to look in the mirror and feel confident about my body. Any tips? Thanks for reading. -Mary