Hello,
I began noticing the same thing sometime in 2009 or 2010. My dr said 'that can happen', but did didn't explain why. I googled starches with HBP, sugar with HBP and menstrual cycle with HBP.
I don't recall the source, but it was a well documented article about types of sugar in the body, hormone levels during the pre-menstrual time period, the stress those hormones trigger and (I think) the body's natural response of releasing more sugar to deal withe the stress.
I have found that when I went on a very low sugar (starches, honey, alcohol etc,etc) diet...my HBP plunged to levels I had not seen in over a year.
This was amazing to me. I guess for whatever reason some people's pressure is more susceptable to sugar instead of salt (I think I'm in that bucket). Additionally, if you research...it seems not all women with HBP experience an extreme noticeable increase in HBP during the cycle.
Do some google searches if you like. Hope this helps.