It's very normal for our blood pressure readings and blood pressure to fluctuate and go up and down during the day as a response to what we're doing and when we get exercise, are stressed out etc.
Normal blood pressure readings are usually for most people 120/80 but even 135 over 85 blood pressure is also sometimes normal.
As long as your blood pressure doesn't get over 135 over 85 then it's not really high enough to be of concern but once your blood pressure gets over 135/85 then it's getting high and should be brought down.
If your blood pressure constantly fluctuates regularly over several doctor visits then it can be caused by some medical condition.
But blood pressure just fluctuating throughout the day or over a few days or so is normal and sometimes your blood pressure will read different from day to day.