Helen I just read this thread. I think the figures in your OP are not outside the norm at all, especially for someone who keeps fit. I am not a doctor, but I have a heart condition now (AF) so I've had to take notice of these things and have read a fair bit on the subject. 100/70 is not bad, I think, and the Pulse Pressure (the difference between the two) is ok. The light-headedness may be due to de-hydration - do you drink while you are fasting? Maybe you don't need to fast anymore? My blood pressure has always been low and now it rarely rises to 100 and is occasionally in the 70s, though usually 85 - 90. I do get light-headed and occasionally have to lean on something for a few seconds but I've never fainted. I think I might faint if I got married though, or I would if my wife hadn't already killed me.
As I say, I'm not a doc. but I'd be pretty pleased with your figures. Maybe give it a couple of weeks being careful, to see how it goes, before deciding whether or not to see a doctor. The fainting may be due to the fasting but I'd guess it is a cause for concern if it happens again.
I loved the pictures of your wedding! Have a happy life!
All the best
Peter