To lose around 15-20lbs / 6-10kgs in 3 weeks? (at least 6kgs)
I don't really care too much about it not being *completelyhealthy* but is it possible?
I have about 11kgs to loose before I become considered underweight, that's according to my BMI...
Also can someone tell me just roughly how much/what exercise I should be doing each day?
Thanks in advance:)

Are you talking about completely losing it or just losing it for a day for such as a wrestling match and you need to make weight? If it's the later of course you can because of 2 words, water weight. I would post this in the fitness area of health & wellness because this is the wrong area :P. You will get much better help in there than in here.

Ok thanks, I thought I had.. lol