I would suggest going up more slowly, like to 15mg instead of straight up to 20mg. When I was on Celexa (the old version of Lexapro), I had to adjust the dose very carefully and take it at around 4 or 5PM in order to not be too tired during the day. Why don't you run taking 1 & 1/2 of the 10mg by your doc?
Love and hugs,
Eddie