I have been experiencing some nausea today as well. I am on Day 5 of a fast that I hope to go 10-14 days on. This is my first fast ever and I am pretty interested in the process and how it has affected me physiologically.
For anyone interested, I am keeping a bit of a log of how this is going over at http://diaryofthefatman.blogspot.com/
(if you check it out, feel free to comment - it helps!).