How Long Does It Take For Bystolic To Work?

I started out taking 5 mg. of bystolic a couple of days ago and my physician told me that if my diastolic number still does not get below 90, to go to 10 mg., which I started last night. How long does it take for bystolic to work? I am feeling exhausted, nauseated and headachey and very anxious about the blood pressure.