Totally normal. In the intial stages of fermentation the yeast are producing co2 as a by-product of eating up the sugars and pooping out the alcohols and other by-products.
Visually active fermentation will slow after about 4 days +/- 1-2 days. This is when the yeast have eaten the majority of the sugars and are not working on the by-products to clean up the beer.
So yes, totally normal. The only way you will be able to tell if your fermentation is stuck is to take readings every 3 days to see if the gravity is changing. If it is not and it is still above your predicted FG then you have a stuck fermentation. If the gravity is still slowly dropping then you are still fermenting and are totally fine.
If you didn't aerate enough you will hit the 1.020 wall. I have hit is numerous times. Pretty much fermentation sticks at 1.020 because you didn't pitch enough yeast, aerate enough or fermented at too cold or too hot of a temperature. Aeration is normally the culprit though.
Best of luck, just be patient. Always gauge fermentation completion by the gravity measurements, not by visual activity or time.