I've never heard of antihypertensives causing low blood sugar, but I suppose anything is possible. Do you get the dizziness mainly when changing positions, like from sitting to standing? If so, you could be experiencing something called orthostatic hypotension, in which your blood pressure doesn't regulate quickly enough when you change position...blood pools in your lower extremities and doesn't get sent quickly enough to your upper body.
As far as hypoglycemia, did you ask your doctors about it? Do you know anyone with a blood glucose meter? If so, you can test your bg when these episodes happen, and that will tell you if it's hypoglycemia. Anything below 70 would be considered low blood sugar.
Ruth