Beejay,
Have you tried feeding at different times of the day? You could try offering a mouse, or a mouse scented rat, or even try a freshly killed/stunned rat or mouse.
Something I have done which works on certain snakes is to dip the head of the rat/mouse in chicken soup. Other methods, which I have not tried is braining the mouse so the brain fluid leaks out, or offering a gerbil.
If your ball is not losing weight and is healthy, then dont be too worried, they do tend to go on extended fasts.
You can read this article for more information:
http://ballpython.snakes.net/
click on comprehensive care sheet
Hope this helps.