Your blood volume in pregnancy increase by about 50%, so that in and of itself can increase blood pressure because it is increased intravascular volume. The body adapts with physiological changes to keep the BP in check. Your body just might not adapting efficiently. Just take your meds and that should work. The doc will monitor your BP. Don't be surprised if you need a dosage adjustment or different med as the pregnancy progresses.
They checked twice the first time than again about 10 or 15 min later
Did they take it more than once? My last visit they said my BP was high but It was because I was nervous and my heart rate was higher than normal too...if you think it's abnormal have them double check it! Could just be a temporary thing.