Oh ya, I had this. Hormones can do this. Annoying, right? Try to rest as often as you can! I tried 20 minute cat naps too which really helped. It wasn't long enough to mess up my night sleep but made me feel a little refreshed. And if you can build at least one super lazy day into your week, I think that helps.
With my second pregnancy, I had a first born who was still a baby to care for (my boys are 15 months apart) so it was hard to rest then for sure.
Here's an article I found in the MedHelp pregnancy articles on sleep issues---
http://www.medhelp.org/pregnancy-health/articles/Your-Pregnancy-Sleep-Problems--Solved/2161