thank you for replying
this is called syncope and number of causes could be responsible
vasovagal/ neurocardiogenic being most common
, carotid sinus sensitivity,
orthostasis( sudden drop in blood pressure with change in posture)
hypoglycemia, seizure disorders, cardiac arrythmias.
given the history of smoking pot, i would more importantly like to rule out cardiac arrythmias.
you need to be seen and evaluated by primary care physician in office.
you also need to be examined for orthostatic vitals, common labs, EKG .
therefore i highly recommend that you schedule appointment with your primary care physician at earliest and get thorough evaluation.
i would be more than happy to answer any questions you have