No, I'm not pregnant! That would be a miracle.
I am on the morning of my third day on the Paleo diet, and for the third morning, I feel nauseous.
Is this typical, and if so, what is the cause, and how long can I expect it to last?
Sounds like the low-carb flu. If it is, then you can expect it to last a few days to a few weeks -- the response is different for everyone. I recommend sticking to the 100-150g range that Mark recommends -- that allows you to meet your body's glucose needs without going to excess, and will allow you to acclimate to beta-oxidation (buring fat) more comfortably.
Thanks for the advice!