I went through the same thing when I was between 6-10 weeks along. Would wake up very early and then couldn't go back to sleep. I finally gave up and decided rather than fight it (and wake up my husband as I lay awake in bed tossing and turning) I would just get up, grab a snack, and work at my computer for an hour or two. Maybe it was the food that helped (I didn't feel hungry). Being up for 1-2 hours would make me sleepy, whereas laying awake in bed for 1-2 hours would not. Thankfully I work from home so my schedule is flexible, and once I was sleepy again I could then go back to bed to "catch up" on the sleep I lost.
Oh, and (knock on wood) after I hit 10 weeks, I was better able to sleep straight through the night. I still wake up frequently, but I can usually go back to sleep fairly easily (without getting up, except to pee!).