Please dont worry (I know easier said than done!)
Your BP is perfect.
The top number is the pressure at which your heart has to squeeze at to get the blood around your body. The bottom number is the point at which it relaxes.
We aim for all adults to have a blood pressure of 120/80 OR LOWER!
This means that at 120, your heart was squeezing at text book normal but is relaxing perfectly. This is evidence that as your normal BP is 105 you were probably a little anxious....but your heart coped so well is was quite relaxed.
A BP that is 90/50 or lower would be low BP and possibly at levels lower than this might you feel dizzy. This happens when your top number is low as your heart just doesnt have the squeezability to oomph the blood fast enough.
I hope this helps.
Every Woman is entitled to understand what happened in her pregnancy when pre eclampsia strikes. I hope to be able to support that process.