Have you told the doctor that you wake up nervous and nauseated? Of course that could be anxiety, but why not call the doctor and see what he says. I'm sure you'll feel better and better each day. I still would call the doctor for reassurance.
Peace and many blessings,
Dosage tolerance and effectivness can be different for everyone. If it makes you feel a bit better, I used to take 30Mgs of Lexapro a day. Stayed on it for 2 years at 30mgs, until it started to fail for me.
Some people think 30Mgs a day Lexapro is too much, but like I said it all just kind of depends on your tolerance to the medication and also your resistance to the given medication.
I can tell you that even when you find the optimal dosage, that it will take a good few weeks at that dosage before you feel better. If the Lexapro fails to produce a full response than you can always discuss with your doctor about maybe adding a second medication to boost the effect.