Relax...first of all your blood pressure fluctuates throughout the day. Second, reread the instructions that came with your kit...everytime i reread mine i learn about something i should be doing that i'm not doing. And third, bring your monitor in when you visit your health care provider. They can check to see if it's accurate---some are not. And there's a thing called white coat syndrome which means some people have a rise in blood pressure when they see their health care provider because it is a stressful time for them. At home, their bps are down.
Hospitals can be scarry places but usually they are full of caring people who do what they do because they've had loved ones who had special health needs. You might tell them you are scared...perhaps they can better address your concerns knowing how you feel. As for the cardio, i have no idea why she is scheduling that. Having worked in a health care environment for about 10 years, i do know that the doctors often prescribe tests that are not necessary because it protects them from liability. I would ask your doc why she thinks this particular test is necessary. Good luck!