Well you said yourself you don't eat right or exercise enough.
If you take care of yourself, eat healthy and moderately with the occasional treat, and exercise regularly, you will notice it's not all that hard. It just takes some motivation. Take some aerobic, and yoga classes.
Now ..if you want to loose that much in a matter of that short of time you need to put yourself on a healthy detox diet.
Drinks: You can ONLY drink water.
Food- Raw fruits and veggies. rice and beans. Plain chicken or fish. Nuts, and chicken noodle soup.
Take a multi vitamin, and any other vitamins or you normally take.
It's definitely a hard diet to stick to, but there is no magic button to loose weight. A detox the only way to loose that much weight in a healthy way.