Besides getting a bigger cuff, you need to check your BP after you have been resting for at least 30 min. Sit down , chill and have your cuff next to you. then always take it 3 times to get a good average. Even getting up and walking across the room to get your cuff can fuck your bp all up.
A nurse had to come take mine and the wifes for insurance policy and I was walking around doing shit, and had been to the gym 2 hours before. It was like 139/75 which is totally off. My resting bp is 125/65