Thanks for writing your query.
After reading your post, I would suggest that you should get your blood pressure and pulse rate monitored as your symptoms can be due to fall in blood pressure.
A CT of head and neck,an Electrocardiogram(ECG) in addition to Hemoglobin
levels will be helpful.
You should lie down with head end lower that your feet, whenever you start feeling such symptoms. This will help in increasing the flow of blood towards brain and will help to resolve your symptoms.
A throat examination by an ENT specialist
will help in planning the medical management for your cough
I hope this is helpful to you.