It turned out that my father, grandfather and most of my aunts, uncles, and cousins were being treated for HBP. My father was diagnosed at 30 after he had a mini-
stroke and one of my uncles was diagnosed before he turned 21, so I know its hereditary.
I've done some cursory research and found that HBP can be caused by a heart valve problem, hyperthyroidism (I don't have), or arterial stiffness.