Question from a confused “high blood pressure patient”

I’m 25, healthy, 175cm tall and weigh about 72kgs (which is inside my healthy weight range of 58~77kg – albeit a little close to the top)

I’m taking a 24 hour blood pressure monitor right now because I failed a previous blood pressure test for my entrance into the Air Force.

Now, admittedly I’m a bit nervous as this test could be the one thing that fails me – no other ailments.

I don’t smoke, drink may one or two cans of beer every other day (did not drink for the past 3 days though), I exercise most of the week for at least an hour… and yet today I’ve had this BP monitor thing on for about 5 hours now and I’m still showing as high blood pressure (140/90+) for about two thirds of the measurements. Basically, I’m bouncing on and off the scale. I spent most of the day working in front of a computer because I have a presentation due tomorrow for my job.

What could be wrong with me OR more importantly, WHAT CAN I DO ABOUT IT?

I have to try and achieve the “normal range” of 120/80

Assuming I can’t take meds (military probably won’t allow that), I would assume I would need to change my diet (which admittedly could be a bit salty but I’m not a huge fan of salty foods either) or exercise MORE – HOW LONG WOULD IT TAKE TO GO FROM 140 TO 120? Can it be done within a month? (That’s all the time that I have)

Thanks for your help!