The thing is with not being diabetic, your liver will respond to lower blood sugar levels by dumping glucose...........
diabetic livers also do this, but our insulin can't stop the blood sugar going to high, and we cant always trust the liver will have enough glucose in storage..
your fast metabolism may be responsible for a lower reading so soon after eating.......has a professional confirmed your faster metabolism....?
does your shakiness and dizziness come with any other symptoms, are you hungry, cold sweats........?