Your systolic number (top) is fine, your diastolic is too low, it should not drop below 60. Add some extra salt to your diet and drink more water to bring it up some. Diet soda is good, it has a lot of sodium (salt) in it. Your pressure can range from 90/60 to 120/80 and be just fine but if the bottom number drops below 60 you need to add salt to your diet. If the top number goes much past 120 it is usually caused from stress
and will decrease when your stress decreases. I work in the cardiac unit
at the hospital and see blood pressure changes all the time, just a little more salt & extra water should help raise it.