My doctor when concerned about my blood pressure had me check three times a day for three months and record it to give to them. It's one way to get a picture for someone with borderline hypertension. Your bp readins you've gotten are borderline but just that and a couple of readings does not mean prehypertension. If you want to track it, get a good home monitor. Put feet on ground flat and arm at chest level. Think peaceful thoughts, take bp and write it down. Do this for a bit and provide information to your doctor
Ways to work on blood pressure if your doctor thinks its okay for you to do so. Exercise. 20 to 30 minutes a day five days a week of activity that raises your heart rate. It has to be in at least 10 minute increments. The American Heart Association endorses this. Also, Look into food choices. The Mediterranean diet or DASH diet are both endorsed for their heart healthy support.
Get it checked by a doctor -- if you're checking it at home, whatever you're using may not be all that accurate. BP does fluctuate. If you get it checked by the doc and it checks out high, you might not immediately need to take whatever medication most docs recommend, as you're young, but you probably in any case whatever you do need to look at your diet, exercise habits, etc.