Hi, there are many causes of dizziness and fatigue after the use of medications for
hypertension such as a sudden fall in blood pressure,
orthostatic hypotension, symptomatic bradycardia.
These causes are related to syncope and pre syncope you reported (fainting and feeling faint). It is important you check your pressure during these crises, write down the values and lead to his cardiologist. Another way to search is to
ambulatory blood pressure and even a Holter 24 hours to assess the possibility of bradycardia (slowing the heartbeat).
In the investigation of syncope we should do an
echocardiogram to rule out diseases such as severe
aortic stenosis, exercise stress test and even a tilt test (patient is lying in a special bed that after a few minutes is placed in standing position for 30 minutes or more).
As you see, it is not something simple, an experienced cardiologist is necessary to define exactly what is happening to you. For now, check your blood pressure, write down and bring to the cardiologist of your choice.
Hope I have answered your question. If you have any further questions I will be happy to help you. Wish you good health.