I'm 12 and I really want to lose weight, now I know I'm not huge but my sister is a stunning blond with a flat tummy. She calls me fat all the time and says its just a joke but it really hurts my feelings and if I ever try to talk about it with my mum she just tells me to stop being stupid and that I have alovely figure. I don't believe her and it just makes me feel worse about myself... *** help :(