I'm on day 10 (I think) on Lexapro. I only had trouble sleeping on the second night, but after that I started taking the pill 30min to an hour before bed. I wake up a bit groggy and I get tired by the end of the day, but I has gotten a little better. You have to see what works best for you and how it affects you. The medication makes me REALLY sleepy, that's why I take it at night.
Hang in there! I know it will get better. Try taking naps through out the day if you can, just an hour or two that might help. Keep distractions away from you like your cell phone or the TV off.