Scaling issue

I have created a character on illustrator and when i try and either scale it up or down, the image does not stay the same.  When creating the character, I used my different tools in order to get it to be exactly how I wanted it.  I used the brush tool, the pencil tool, as well as using different strokes and filling in certain areas.  Now when i go to make it larger, either the colors inside the outline no longer reach the outline, or the shirt for example is no longer fully filled in and I can see the white background through little holes in the colored area.  There are many many sublayers within the full layer of the character.  I'm not too sure if that means anything or how I could make them all one layer so each time I drew something using a new line or tool, they are able to stay together.  Can someone please help as I was not able to find any resolutions to my issues.

thank you