Blood pressure dropping

My blood pressure was 102/59 its never this when im at the dr its always like 120 i think because my nerves. But i get symptoms of lightheadedness and super thirsty and dizzy. And feel a strong wave of sleepiness. But everytime i go and tell them its perfectly fine. Iv fainted once before. Earlier in this pregnancy. Im 24 +5 days shouldnt it start rising a lil in the third soon??