I was wiped for the first 2 weeks, almost felt like jetlag, I wasn't sleeping at night and then that rolled into the next day, when I had to go to work, then in the evenings when I felt like crashing into bed, I then couldn't sleep again!!
But in time it eased and my sleeping pattern balanced itself out!! Then I slept ALL the time, 10/12hrs at the weekends, must be our body/mind just needs to catch up on some much needed rest!!