It's perfectly normal, especially if your body is burning through its own reserves! A human at under 10% body fat still gas tens of thousands of calories of energy stored. If you're burning through your own fat, you'll be getting many calories from that alone.
I would not advise fasting for over 36 hours, though, as you may become deficient in certain nutrients or upset your body's natural rhythm, so try and eat a little. It isn't a certainty, but some people are at risk of random problems when they fast too long. If you feel fine fasting for over 36 hours, go ahead, but I wouldn't recommend it. Most of the time, though, fasting is fine.
I rarely talk to people about Paleo/Primal, but, when I do, it's when they're NOT complaining about their weight or health.
You see, I don't really "do" pity. And one thing I've learned about people is that they're more open to suggestion when they're happy and stable. When they complain they only ever want pity, not to be advised.