Can't sleep through night

Hilary
It's like clockwork. I wake up every morning at 5:15 --wide awake. Except yesterday. Yesterday I woke up twice at 3:30 and 5:15. I've been going to bed around 11 and I'm usually a solid sleeper for 7.5-8 hours. 
I'm only just over 4 weeks. Has anyone else experienced this? It's driving me crazy because I'm wiped by dinner time.