First off, stay away from the detox drinks. They are overpriced for what they are... they do NOT detox your body, they simply mask THC in your system, and today's tests often pick them up and they will know you tried to dilute/mask. Like Weed420 said, with all the flushing you are doing, drink a big Gatorade the morning of. It will help keep the specific gravity of the sample within range. If you want that extra reassurance, then check out this thread:
How I Pass My DTs in 24h or Less
Having used this method to pass two tests now, with one of them being a random in which I smoked three times the previous day, I am pretty confident in it. In the preceeding 24-48 hours, DO NOT WORK OUT. This burns fat cells that may still have THC stored in them and releases them to your bloodstream.
Per the method outlined in the above link, basically:
Take the vitamins listed. wait about 2 hours until your piss is dirty looking. Then FLUSH FLUSH FLUSH... up to 4 quarts of water and a big gatorade. When you start peeing clear and lots of it, back off of the water intake significantly and take the last dose of the B complex, which will bring back a natural color to your piss. You can do this whole operation in about 4 hours. If you really, really want to be sure, do it several days in a row before your test, though most likely you will pass just as you are. 5 weeks is a pretty decent clean time. Also, don't worry about the large quantity of vitamins you are taking. Your body will absorb as much as it can, and pass the rest harmlessly through your urine. Niacin is the only thing you need to be careful of.