Sleep

I am not quite sure why but for 3 days now I have been up at 4 a.m. and unable to go back to sleep. It is getting frustrating because I need my sleep. I am 34 weeks pregnant and will soon have a little baby to keep me awake at night. I need all the sleep I can get right now. Any suggestions on how to put myself back to sleep for the 2-3 hours til the alarm goes off when I am stuck awake?