weight problem

So I'm a twin and I've always been the fat twin. I know because my mom always buys my skinny sister candy and junk food but never me, and my mom would always make me and only me go on walks around the neighborhood at night and make me feel bad for eating good food. I lost a lot of weight on the past year and I'm proud of that but I still feel like a fat blob and I'm ashamed. Me and my sister are asking for bathing suits for our birthday (it's one bathing suit but they are rather expensive) and I know that it will look incredible on my sister but I don't know about me. Is there any way to feel good about your body when you're constantly comparing yourself to others?