Sorry about your nausea. I have a friend who tried the Master-Cleanse and had a very bad reaction to it...she ended up stopping because she couldn't tolerate it. It's hard to work full time when you're spewing your guts out.
You may want to try a different route, like juice fasting. If you're determined to continue, I'd back off for a few days and take the lemonade as a tonic to see if you can tolerate it before returning to the full regimen.