I have the same problem. The other night i got a solid 8.5 hours sleep and i still had a nap during the day when DS was asleep. Just rest, Take it easy and PLEASE listen to your body. Also drink water, I have a hard time drinking water as i dont like the taste so i struggle to drink 5 glasses a day. I argue with DF that mineral water (flavoured) and 1-2 cups of tea a day is just the same as the water i miss out on!
Take care,
Jenni