Congratulation, you’ve hit critical limit. Your blood sugar crashed (below 55 most likely) and your sugar stores were depleted. At this point, your body has trouble bailing you out. If you continued, you would risk doing harm to your organs.
You are either: Doing these fast too often without sufficient nutrition to support the fasts OR you have a monster in your pancreas called an insulinoma. I’m leaning towards the first one but it wouldn’t hurt to have doc review your concerns.You could buy a glucometer from pharmacy and check sugar levels throughout one of your fasts at home. Mainly checking at start and once symptoms start. That may give you some insight if you can’t get into the doc soon.
I wouldn’t do anymore fasts unless you have someone around you constantly that is aware of the situation and can act upon you potentially going hypoglycemic.