Yep all normal!
I started my Mat leave basically two weeks ago and the first week i was feeling great, reasonable amount of energy and then it hit me this week, Monday i got up for an hour then i was asleep on the couch for another 4 hrs i think, Tuesday and Wednesday was the same. Today i was up with DP and even had brekkie with him so the energy has kicked back in again. Oh another thing is it doesn't help when you go to bed at 11pm then the loo calls at 1am, 3am and then again at 5am

Our bodies need all the rest we can muster for when we won't be getting it LOL!