I did have that problem during my first and second preg. I did best in my tilt back chair that had a foot rest. I found not laying down all the way helped me the best during those times. I had to have the tv on and my favorite program was Frazier his voice late a night puts me to sleep. I also drank tea (decaf, herbal) I think I craved the heat more then anything but it seemed to help as well. Classical music also helped at times as well a bath not shower helped me at times. I have to try different combinations all the time. I also walked in the evening before i started my bath and some kind of routine to try to get to sleep each night. I think it's mainly hormones, I had never thought to ask for something for sleep didn't know I could get anything.
My niece sprays her bed with lavender has it all around her bedroom she's due in Dec 2009 and says that's what helps her, she also has an air purifier in her bedroom give it much credit (the noise and better air to breath she says helps her right now. Oh, she also has a foot soak machine that vibrates she uses on the bad nights (of not being able to sleep) that helps her also.
I hope you can find something that helps, soon.