Ok so first off I recommend looking at weooweoo's art (i think). He makes easily some of the best cartoon heads.
So comparing to his art is how I will be giving this Cnc so it may be harsh and a lot to take in, but trust me this will help <3.
So, first of all, is the shading. I am no even going to say anything on this. Just watch
this video made by Calamity.
Also watch
this video for anime hair.
And
this video ;p
The second vid is kind of a step by step, but practicing can help tremendously.
Also, stop using the pen tool, try drawing some basic reference sketches on paper and either vectorizing it in Adobe Illustrator or Adobe PhotoShop.
If you do not have accessibility to these programs use gimp preferably.
Then you cant trace some of your smooth linings over to digital art.
If you have a draw tablet this is an unnecessary step, just draw smooth with the tablet instead of making blocky shapes.
This was not a whole lot of cnc but I hope I could help.