I just read back to some of your posts - and am actually taking back the advice to even use this even for an event.
I think you need to sort out a livable, healthy diet. In earlier posts you mentioned eating sweets during the day, and in this one you mentioned fast food - neither of which are getting you the nutrition you need. If you want to get into fantastic shape, you need to eat a healthy, balanced diet so your body can function at it's best. I like to think of it as what kind of fuel you would put into your car - what helps it function the best. Not the crappy, cheap stuff, right?
This may fall on deaf ears because you seem to want to strive to be underweight, which implies a distorted body image. I'm not saying this is 100% the case, I am just basing it off what you've written. Anyway, there are plenty of sites elsewhere where you can find whacked out ways to lose weight, but I don't think you'll find people endorsing any crash diet methods here.
(Sorry to sound harsh, btw. I've struggled with food/body issues in the past and know it's not easy when you don't like what you see, but you really need to put your health first).