Vicious cycle

I am 31 weeks and I am in a vicious cycle of being starving, to being so full I need a nap, then waking up hungry again !! It's awful. I am turning 30 years old tomorrow, this is my third pregnancy and I have never in my life had so little energy!! I still have so much to get done before our son arrives and so little energy to do it. Hope I have a final burst of energy here sometime.