Yes this happens to me a lot and I have stopped worrying about it.
An A1C reading of 5.5 or 5.5 is good. The reading for an adult should be between 4 and 6.6, so yours look good.
After a lot of research I discovered that the A1C test takes an average over a 3month period. The last time I had my A1C i had been monitoring my levels at rhymes home as follows 5 times a day take readings, add the readings together and divide by 5. Keep the daily averages for a week and again add together and divide by 7 that will give you the weekly reading. I did this for 3 months and when I had my A1C results from my doctor she said it was 6.3 and my readings said 6.5 so I was not far out.
With regard to fluctuation of readings again it is the same for me i.e. yesterday my readings were a bit high but today back to normal. I have also learnt that readings can change in a matter of minutes. I guess its part of being human .
In case you are wondering I set up a spreadsheet to record my hundreds of readings.
Finally dont always believe what you read on line there is often bad and misleading info.
If my doctor was to say to me your OK then that is what I would go with.
If you need further information or detail please let me know.