Hello
Welcome to health care magic.
It is right that blood pressure of 100/70mm Hg is normal for someone who has no symptoms.
However,stress,standing for a long time or
hypoglycaemia are the factors which can affect easily affect such person and cause
nausea and
dizziness.It may be then causing your BP to fall till 90/70 mm Hg.
Other possibility of low BP is nutritional problems/certain medications/endocrinological problems.
Some measures you can follow is
I advice to get your blood haemogram done for ruling out
anaemia.
Maintain hydration of your body by increasing intake of water.
Dont skip meals.Have healthy diet.
Minimize physical and psychological stress.Regular yoga and
meditation will help.
Still if the symptoms continue,visit physician so that proper detailed medical history is obtained and accordingly further referrals can be done.
Hope I answered your query.
Any further query is welcome.