I'm on Lexapro as well and stillnocht at night, trust me I've tried everything you could think of to help, acupuncture, hypnosis, meditation, group therapy, CBT, I'm getting counselling at the moment.
I have been lowering my dosages very slowly as well, must be over the last 6 months, going from 10mg down to 3mg. Every time I get down to a low dosage I get a rebound effect.
You need to be honest with your doctor that you are not tolerating the taper. It may be as simple as slowing it down! How fast is she tapering you, what doses has she dropped you to and in what timeframe? With benzo tapers, the slower the better. If you are honest with her that you agree with the taper but cannot tolerate the symptoms, maybe she will adjust the taper for you. If not, I would suggest looking for a new doctor.
Are you on any other meds? Have you tried any other medications? Has your doctor ever spoke to you about trying either an SSRI type antidepressant, or even a longer acting benzo, like Klonopin? There are definitely options out there. How about therapy, are you doing that?
Let us know how your talk with the doc goes, best of luck!