how to loose weight quickly?

ok so its my moms weeding in march, and I need to loose weight. im 78kg and 14 :( = not good. im about 5,4 in height. I want to loose quite a lot of weight. im extremely self conscious on my body. I hate it. I hate swimming cause I hate showing my body. I hate not being able to wear nice clothes that other girls wear. I know its my fault but I cry myself to sleep sometimes cause it hurts me. I have been bullied and have self harmed in the past. - I don't do it anymore! but im ready to take action and take control of my life. I would like to loose weight before march 1st 2014. and I want to loose a lot of weight. FASTT!!!!!!! but im not quite sure how to do it. I have tried fast walking and dieting but It doesn't work. my body cant get used to it.. Help!