The easy answer first. It's a little like baldness versus alopecia. Now to your blood-pressure readings. It's good to hear that you're monitoring your own blood pressure. Readings you take yourself could pick up subtle changes earlier than if you waited on a periodic exam.
Hypertension is the prime reason for monitoring blood pressure.
At some point, as you release the pressure in the cuff, the blood will just start to flow. This causes a sound to begin and marks the level of the systolic pressure. And as the pressure in the cuff gets less and less, the artery will fully open and the sound will stop. This marks the level of the diastolic pressure. Blood-pressure readings are notoriously variable for the same person, depending on time of day, location, degree of excitation, type of instrument, etc.