Oooo, I absolutely hated this part of the pregnancy, everything was fine until i couldn't sleep. Unfortunately it is just one of those things (it also doesn't prepare you for feeds at night at all, the feeds are easier). I ended up sleeping with my ipod on quietly as i found a lot of it was that i just had too much running through my mind, so i would listen to my fave tunes and i would eventually fall asleep. I don't think there is really anything that you can take. Really try to sleep in but more importantly try to take a nap in the day. I always found it so much easier to sleep during the day, not sure why maybe it was because i didn't want to. Take as many naps as you can, once baby comes you won't have the luxury of doing it when you want to (i haven't had a daytime nap since DD was 1 week old, she didn't like to sleep in the daytime). Hope you get some rest soon, it is a horrible horrible thing not being able to sleep.