First of all you are laying too much base colours which has resulted in the stronger colours being weakened, what you need to do is limit the strength of the white and light grey. The angle of the nose is slightly out of line and the outline of the right eye is not quite rounded enough. But having said all that you have done very well and I would not alter the picture you have done rather take all these tips onto your next project, remember you learn from every picture that you do with the pastel pencils.
What I would do if I were you is keep this Kitten picture without adjustment so that you have a yardstick for future projects you will see the difference with every one you do from now on. The Draw and Paint Cats & Dogs DVD will help you enormously but when you can join our members site I am sure you would enjoy what we have on offer there.