BP absolutely changes throughout the day, with stress, with what you have or haven't eaten, if you have just rushed down the hall, etc. Another issue to consider is the accuracy of the BP unit involved. Usually, before a diagnosis of high BP is reached, a person is assessed through wearing an automatic BP device from the hospital that measures you BP at timed intervals throughout the day for a few days. This is because some people actually experience something called "white coat syndrome", where the stress of seeing the doctor artificially RAISES ones BP. My dad has this. He saw his regular MD, who took his BP 3 times in the office, diagnosed High Blood Pressure and prescribed pills. Dad took them, and that afternoon passed out flat on his face because his BP was NOT high at all and the meds kicked his BP way, way down. The MD who diagnosed him was about 105 years old ("we've known Dr. X for 45 years now, and go to him for EVERYTHING even though he can't see so well anymore, dearie...") and wasn't aware of the protocol.
SO, IF you've seen your MD, and your MD has taken your BP and it is fine, stop messing with the machinery! The machinery is to indicate if you need to see your MD as it MAY indicate a problem. You have already seen your MD. I'd leave it at that!