Exercise will raise your blood pressure during the activity but after you've rested your blood pressure should actually decrease and cardio will lower your BP over time. You might be a lot worse cardio "conditioning" shape than you think. Even if you're thin, it doesn't mean you're in good shape. I would definitely see a doctor but I think you better start doing cardio everyday but because of your BP skyrocketing, I would start very very slowly and work your way up.
You might also want to take Hyysop, Hawthorn Berries, Fish Oil, CBD Oil, Rosemary and eat celery daily. I take these. Blood pressure medicine for me is horrible and will probably make you feel like crap. Change your diet and exercise (especially cardio, daily).
If you have not already seen your doctor you should. Just going up and down 2 flights of stairs should not be enough to raise you pressure that high, Yes, you are in a danger zone. Once you and your doctor address your high blood pressure, exercise is a great way to get it lower.