I am 21 and have high systolic (148 +) and low diastolic (35-40) blood pressure, what does this mean?

Abnormal BP. That blood pressure is abnormal especially for one so young. Verify that your BP apparatus is functioning properly. If indeed that is your true blood pressure two things come to mind: aortic insufficiency which is a back flow of blood across the aortic valve or severe anaemia. Please see your doctor about your blood pressure.