I'm a bit concerned! Have been having trouble with the website. My lessons of yesterday have not registered and only three of the five I have completed today have registered. I'm back to one day and was on 9!!
It's all practice so all to the good, but a bit disappointing.
When you're done with your lessons, don't leave the website immediately. Make some tabs load that you haven't loaded recently (such as the lingot shop, discussions, etc.) so that you force a connection between your computer and Duolingo's servers to make sure they record your progress. This is also very important to do with the mobile apps.