Why does my weight keep fluctuating when I'm eating right and exercising? I should be losing weight!?

I've been eating right (lots of ice water, fresh fruits, veggies, chicken, tuna, fat free yogurt and fat free cottage cheese mostly). Very few carbs. No white flour or sugar. My weight was 173 to start. Now it keeps fluctuating between 167 and 172. I don't understand! I'm walking/jogging twice a day (about 3 1/2 miles per time at about 4-5 mph). I'm taking green tea pills, green tea acai water pills, hydroxycut max and Jillian Michaels detox and cleanse pills. Any suggestions? I need to lose 15 lbs by July 20th or be down to 155 lbs to win a bet! Thanks!