Hope your BP regulates soon. Can't say if it's MS related or not though since my family runs on the low side, I actually was concerned before my dx since it was running up in the 140s/80s. Though another thing to keep in mind is that it's not just the top number that means high or low BP. It's really the spread between those numbers. 120/80 is considered normal, the systolic pressure is 120 (contracting), and the diastolic pressure is 80 (resting). A "healthy" BP is when the contracting pressure is 1.5x greater than the resting pressure.

So for someone who exercises a lot, runs marathons and such a BP of say 80/60 is healthy (if my math is right ) or even 45/30 could be "healthy" for that person and the amount of exercise and training they do. A low BP could also be 120/100, or a high BP of 120/60.

What they're really looking at is how much blood is filling your heart when it's resting, versus how much pressure it is then exerting in sending that blood through your body. If your heart is flooding with blood in rest (diastolic pressure...bottom number) but barely exerting any pressure in contraction (systolic pressure... top number) then it is considered low. Conversely if your systolic pressure seems to be squeezing every last drop of blood from your heart, then your pressure is high.

The 120/80 "rule" is really just an average of what middle-aged American's in fairly good health and shape were running back when they came up with the gauge, sort of like BMI taken from a simple height-weight chart, there are far too many factors to take into account for accuracy, but if the average person wants to check themselves for any potential problems, well there's a highly basic guideline they can look at.