Maybe you used Illustrator, if you did you don't know how to use it. Sorry but that's what i think at the moment.
For me it seem like you used the paintbrush tool where you should have used the pen tool. I've never really used Illustrator but your skins look like you used paint not a vector based program like Illustrator.
Your skins are not bad you have good ideas you just have to learn how to use the tools you have