What Causes Fainting Episodes While Treating Sinus Arrythmia And Bradycardia?

Question : I'm a 68 y/o male with controlled HBP and high cholesterol. Recently I've been having palpatations with occasional "grayouts" and faintng for a few seconds. I've had an EKG, worn a monitor for a week , echo cardiogram, I wear compression socks , which seem to help, I take a supplement with taurine and magnesium and argenine which seems to lessen the duration of the episodes. I know it's anxiety related so I try to reduce stress.B ut I've noticed after a meal I get them without fail, especially a heavy meal. I'm 5' 6" weigh 160lbs and moderately active (tennis once a week, pliates 1/week and walk 20-30 minutes a day, bike 1/week 6-8miles). My cardiologists doesn't know why I get these fainting and grayouts . Any ideas. He said the ekg and monitoring are normal. I do have a sinus arrythmia and bradycardia but no atrial fib.