Have hot flushes, sickness and sore boobs replaced that initial glow?
This is not just your run of the mill, 'I've had an exhausting day' tiredness, but the kind of tiredness you get when you're coming down with flu, where you imagine that if you close your eyes you'll fall asleep on the spot and not wake up for 24 hours!
Help yourself... by learning to relax. Give yourself time out and take little naps. Going to bed much earlier than usual and not scheduling anything for a few weekends can also help with your energy.