What Causes Severe Fluctuations In Sugar Levels?

I am 53, and have been experiencing spikes in sugar levels then drastic quick drops. the feeling is often like being drunk. when the levels drastically drop I often have a a loss of memory, get sleepy or groggy. I am not diabetic (that I know of). I did go through some testing years ago and was told that I was hypo? or hyperglycimic and that I possibly had a hyperactive nervous system. I am really not sure what is going on.