You didnt mention your age , othewise it will be better to understand the problem.
As you are suffering from high blood pressure
. as you mention the diastolic pressure is 116 it is too high and dangerous for health.
but it is ok as you are on treatment .
the feeling of imbalance may be due to Fluctuation of blood pressure so you should go for regular blood pressure check up till the blood pressure maintain the static and normal level.
imbalance feeling on standing may also be due postural hypotension
for further evaluation you should visit again to your doctor