high blood pressure and dizzy spells

I am a 77 year old male - 5'10 160 lbs.  High blood pressure runs in the family and I have been on meidcations for years.  I started having severe dizzy spells almost 2 years ago and was finally diagnosed with a blocked left Carotid.  Had this cleared in July and all was well.  THe dizzy spells started again even though they lowered my blood pressure meds - which they said was causing the problem.  No one seems too concerned or willing to find out how to fix this.  My blood pressure runs in the 140/80 range but during a dizzy spell it bottoms to 105/60 or lower.  Could this be caused by something other than my meds?  they have cut them, raised them, all without relieving my dizzy spells.  I was told and read up on Kidney issues causing similar symptoms - should this be my next request for testing?