Its the dreaded pregnancy insomnia :) a nice warm bath, a nice warm cup of milky hot chocolate or chamomile tea and a very boring book :), if you wake up during the night just get up and go with it, have the tea or h/c again and watch abit of tv, then if you can have abit of a lie-in in the morning
You could go for a 30-45min walk in the late afternoon so ur body becomes tired when it's time for bed. Or you could ask ur dr. To prescribe you something that will help you get some rest.