For a long time, the standard for "normal" blood pressure was 120/80. The current thinking is that a more healthy pressure is actually 110/70. 106/64 is a little lower than the norm but may be totally normal for you. If you become dehydrated it can lower your blood pressure and if your blood pressure goes too low it can cause feeling faint or passing out. If it's never been an issue and your MD doesn't have a problem I wouldn't worry.