What you suffer from is probably a vasovagal syncope or a vasovagal attack. The complex group of
symptoms are mediated by the vagus nerve. This nerve is irritated by prolonged standing, standing up suddenly, stress, pain, hunger, dehydration, intense emotion etc. A tilt table test, holter monitor, echocardiogram etc are done for confirmed diagnosis. Discuss this with your doctor.
There are many causes of dizziness, lightheadedness, passing out, blackouts etc.