Its such a different experiance to have such scary new things happen to us when we are usually strong and healthy,and until it actually happens to you noone could possibly understand what it is like to suffer this.I know i was totally oblvious to anxiety and depression until the doctor told me i had it,i thought all these horrible symptoms and fears cant be down to that surely and i kept going back everyweek until i was convinced,it is good that you are in therapy,it wont happen over night but with determination you will start feeling yourself again.
Lexapro is one of the newer meds and along with Cymbalta, most people that I've spoken with seem to adjust and feel "normal" again after about the first month. If you're 3 weeks into it, I think you should start feeling the full benefits in about another week. Good luck!