My fasting glucose was 67 and my dr is not concerned. i've been feeling very tired lately and at times shaky. should i be concerned?

Probably no: The lab finding by itself is completely normal, albeit on the lower end of normal. There are many causes of feeling run down that are more likely to be related to symptoms (stress, sleep deprivation, irregular meals, etc). Do any of these sound like you? Try focusing on getting good nutrition/hydration, sleep, exercise and see if your symptoms improve. Good luck!