Each time I changed doses of Lexapro, I would have a little anxiety. But, I did have a few valium to use when I went somewhere really stressful! I would guess it took me a week or two, to hardly have any anxiety. Just remember different meds work differently for different people!!!
Oh yeah - about the sleeping problems. If I took it too late in the evening, I would have trouble sleeping. You need to take it either morning, noon, or early afternoon (say, 4 or 5 at the latest - of course it also depends on when you go to bed and how early you have to wake up!).
I hope you find a med that helps you, be it Lexapro or something else.
Take care. Wannabe