Blood pressure naturally rises and falls during the day. There is no set pattern.
Food eaten, stressors, or lack thereof can all account for changes in BP.
So can the position your body is in (when pressure is taken)change the blood pressure reading(also whether or not you speak during the reading).
It is common when consuming an acidic diet (soda, meat, eggs, flour, sugar) to have significant changes in heart rate.
I suggest you look into your acid /alkaline balance and do a web search or read the form here at curezone.