I get pretty bad insomnia too.Â
With my first pregnancy, I would fall asleep no problem, but would wake up early (4am)
This time around, I just can't fall asleep, sometimes im up until 3am! And DH gets up for work at 6... :( It makes me SO tired (duh) and so cranky!  I have kind of given up on sleeping at night like I used to. I sleep whenever I can, whether it's during DS' nap, once DH is back home from work, etc.  I had tried everything, tisane, hypnosis, warm bath, unisom (it gave me restless legs, it was so much worse!!)...Â
I think that thinking too much, having so much to do (not really stress or anxiety, but just nesting, wanting to research stuff, etc, as PP mentionned) is really what keeps me up. I now take full advantage of being awake for a few hours after everyone has gone to bed to clean, sew, cook, research stuff. Once I've done a couple things and feel like i've been productive, I find it's easier to fall asleep.