Can't get enough to eat....?

I'm 31 weeks and for the past few days I haven't been able to stop thinking about food and I have been hungry all the time even though I'm eating. For example, I've only been up about 4 hours today and I've already eaten 2 1/2 bran muffins, a boiled egg and a 12 oz smoothie. I'm already thinking about lunch! Is it normal to get such a surge in appetite around this time in your pregnancy?