Quickest way to lose weight for teens?

Hello, I am a 15 year old girl, I am about 170cm tall and I weigh 13.8 stone. I look like an ogre and I genuinely am disgusted with myself for allowing myself get so disgustingly large and hideous. I really do not know why I didn't start to make change earlier, rather than now. I hate myself for looking so unhuman and horrible. I would really really like to lose so much weight as quickly as possible and I am so willing to put in the effort. I want to be pretty. More than anything. I don't get bullied at school, I actually get along very well with everyone, but I know that people think I am fat and ugly. I was hoping somebody could offer me tips on how to lose weight? I rarely exercise and I realise that I MUST make time to exercise and I must stay away from snacking and eating unhealthy foods. I throw up sometimes but it doesn't do the trick. I'm actually crying at this very moment just looking at myself. I think my depression lead to my obesity. I live with my grandmother as my parents left me when I was four, I sometimes think why I cannot be perfect and why I had to be the ugliest person to exist. Being 15 now I have never gotten over the fact that nobody wants me. I haven't officially been diagnosed with depression but I reckon I have it. I have attempted suicide three times and I self harm regularly, I am just so sick of being me. Please help me. I just want to be accepted. To be normal. To be beautiful. Thank you.