Thanks for your writing your query.
After reading your post it can be considered that the fainting
attacks are due to low blood pressure.
Your recent blood pressure of 107/55, is in the lower range and any furthur fall can cause weakness and fainting (in severe fall of blood pressure).
You should consult your treating doctor and discuss for dose adjustment or change of medicines you are taking.
Also get an ECG done and a 24 hour recording from ambulatory blood pressure
recorder. This will help to know the blood pressure at the time of fainting episode, if any. Also get a scan of head done to rule out other causes of fainting.
If you feel weakness, you can sip or eat small amount of salty drink or food as this will check furthur serious fall of blood pressure.
I hope this is helpful to you.