You should sketch in more of the body. Drawing necks in isolation never ends well.
If you look at ref closely, you'll likely find that necks aren't a simple shape. In the front, they actually get narrower towards the bottom. In the back near the spine, they also go "in" a bit. But then they have the narrow muscles that come out frontward a little from behind the ear, but come together at the collarbone, and there are the muscles that connect the neck to the shoulder, which also give the neck a wider base on the sides towards the back. I probably explained it weird,
here's an image. I recommend looking at lots of ref, to build up a 3D mental image. 2D doesn't do necks justice. Remember, you probably also have your own neck you can look at.
Here's another sketch to give you a rough idea of what I mean, but I don't recommend following it, it's been a long time since I did a proper neck study. Do your own studies so that you can understand what you're doing and how to simplify it. You probably have your own ideas about how soft/muscular/tendony you want this character's neck to look.
![](http://i.imgur.com/wNm8XzA.png)