Pregnancy has the tendency to “reset” many body systems. Looks like you got pretty lucky in this regard. Hard to recommend, though for the middle aged male borderline hypertensive.

I went through the very same thing at age 19. Doctors briefly thought I had a type of cancer called pheochromocytoma. Wrong. They then told me I had transient essential hypertension, which basically means in lamens terms, you have high blood pressure that cormes and goes and we dont know why. Man, it cost a lot of money to get to that diagnosis. I went through a basic try this try that with blood pressure medicines for a while and they settled on one with th least deleterious side effects. I was on an ace inhibitor for years before I quit them at 27. I’m now 29, I keep my blood pressure checked often and notice brief increases occasionally but nothing to stress. As for what caused my transient essential hypertension? My theory is possibly heavy weightlifting and or stress. My recommendation is to keep an eye on it, keep a chart of your pressure through different times of the day as your circadian rhythm will affect its levels at different points on the cycle. Eat healthy and exercise and do not go on blood pressure medicine unless there is absolutely no other option. They tend to have many side effects.

There was some tension at work or with any partner or some kind of apprehension that you could not gauze.It could be that some change in dietary habits then and now and a change in living style that caused flexibility in your blood vessels.It could be that now you are more at ease with yourself than what you were in those days when the bp rose a bit.

There are the “weird” causes of htn at your age.
White coat hypertension ( being scared of the doc)
Pheochromocytoma
Carcinoid
Certain Drugs.. such as antihistimines
It could have been anything…..
I wouldn’t worry if you are consistently running at 118/68.