korvette and greenpriest024 are right on. You need to increase your metabolism. If this is really important to you, do the following:
Exercise- Cardio and strength. Keep it light if you have been sedentary. Walk every day gradually building up to a light jog for at least 30 minutes. Do some beginner type weight lifting but DO NOT OVERDO IT.
Diet- Eat small meals several times a day. Try to stay under 2000 calories/day. KEEP AWAY FROM THE JUNK FOOD. Fat is your enemy in this endeavor.
Don't waste your money on 'cleansing products' and for God's sake don't drink any Ajax! You can also submit, at your expense, for your own private test right before your deadline. If you're still positive maybe you can contrive an excuse (out of town funeral). Best of luck.