How can i lose weight in 3 weeks and get a six pack?

Loosing weight too: fast can be dangerous. See your doc first, and then consider lower carb and higher protein intake. Exercise daily if possible, even brisk walking 20-30 minutes is helpful. Above all, like yourself and others no matter what the scale says. Peace and good health. A trainer at a gym can help w/a program for your "six pack" and overall fitness.