I can tell you from my own experience I had the same thing. Not only until I began to understand it and learn how to control it did it start to subside. I also take Lexapro and it took a good month for it to fully get into my system to begin to help me. It was tough, I won't lie but once you learn more about anxiety and better understand it, the easier it becomes to realize when it's happening and how to calm yourself down. Don't get me wrong, it doesn't just go away, it's always there but in a much more manageable state. Hope that helps you a little, it does get better.
Jenn