essential oils during pregnancy...yes or no???

I am at the end of my rope with not getting any sleep. I'm so exhausted every day but yet at night I can't seem to fall asleep and when I finally do i maybe get an hour or 2 before I wake up and then can't get back to sleep. I get maybe 4 hours of sleep a night and I don't nap during the day. I've heard that essential oils can help but I'm wondering if they are safe to use in a diffuser while pregnant? anyone have any info? I'm getting desperate...