can my low blood pressure cause physical symptoms similar to depression?

i have had low blood pressure all of my life.  i am not overweight, i enjoy exercising and know that sport can help raise my blood pressure.  i have, what i can only describe as brain fog and lethargy. i am often dizzy and have fainted a few times. i also have migraine attacks and as i get older, it has got worse(am now 47).  when i was pregnant i had the opposite and my blood pressure was very high.  the side effect from this however was that i felt really brain fit.  i had no problem with my memory and i could think clearly.  i take anti-depressants from time to time but i take them to help me with my lethargy and as i don't like many of the side effects, i try not to take them for more than periods of 6 months........ i have never felt depressed or suicidal.  could there be a connection between my low blood pressure, brain fog and lethargy.  my heart makes extra beats when i am laying down and the heart doctor said this is probably because my blood pressure is too low.  i am not an athelete but my basic fitness level is good and  apart from dizzyness, i tray daily to be active.