Always have low blood pressure, around 80/50 to around 95/65. teenager; shouldn't it be higher? suffer from fatigue, have exams soon, what should i do

See below: For a teenager of average hight and weight a systolic BP less than 90 or diastolic BP less than 60 is considered low. But if the teenager is underweight, blood pressures below these numbers can be normal. If the blood pressure cuff is too large it will give falsely low readings. Fatigue is usually not a sign of low BP. Lightheadedness, near fainting or dizziness would be signs of low BP.