Fainting Frequently, Dizzy, Fluctuating BP. What Could This Mean ?

Hi My name is AAAA, for the past year not i have been fainting at least four time a week possibly more depending on my day. I have been to a Cardiologist for a few months did all the test, They concluded i have syncope . I can not drive nor work. I get dizzy when i stand, was on blood pressure medicaton and that either made it worse or did nothing at all. My blood pressure does flucuate when i stand and sit. At times i know when i am about to pass out, other times it happens suddenly. They could not conduct a reason for this, another option i may think is it could be POTS. But ihave not cleared that with any doctor. I just want your opinion on to what i should do. Should i see a neurologist? Or what could this possibly be? Thank you for your time.