Majority of patients will feel some sort of discomfort during the first few days of Invisalign treatment. Thereafter, the 'pain' will tend to subside before the next set of aligners.
I wouldn't be completely surprised if you do not feel any discomfort. First and foremost, some patients do have a higher threshold of pain, hence they do not feel anything during aligner treatment. No pain does not necessarily mean no movement. Sometimes it could be that the first few aligners put less pressure hence the level of discomfort is very low.
If you are able to move onto your next aligner seamlessly without too much discomfort, this means that your teeth are moving nicely. Lastly, if you are still unsure, then do check with your orthodontist who will be able to reassure you if things are moving nicely.
Hope that helps and good luck!