I understand your question, but I *think* the real question you are asking if whether or not you should be concerned about possibly having diabetes. If you had fasting blood glucose readings of 138 and 140, then the answer is "yes"... and yes, your diet and eating habits certainly can have an effect on your lab tests. But: the A1C is essentially an "average" of the amount of glucose loaded on your blood cells over the past 3 months. So, while it could be possible, I suppose, to have daily huge spikes and daily huge lows that would produce a "good/normal" result, I think you would have had more pronounced symptoms, and an A1C result of 5.1 sounds good (the 'normal range' depends on the lab doing the test).
Bottom line: the best way to help prevent blood sugar issues is to eat a healthy diet with meals eaten at the same time each day (optimally several small meals a day). It doesn't sound like you "need" to be on a low-carb diet, but lower-carb sounds like it works for your body, so just cut out the "bad" carbs (starches, white flour, minimize desserts and junk foods), up your intake of leafy green veggies and fiber, and keep an eye on your weight and as it sounds like you have a meter, keep testing and see what effect your diet/meal choices have on your blood sugar.
what my question is since i was not even eating normally in the first place and was under eating before i had the glucose test and got put on the low carb diet could it have affected my a1c level test and made it show low as opposed to eating 3 meals a day of a a reg carb diet where it could have had a higher a1c reading