With much respect to Pied3, if I might add my happenyworth on this page - Flash MX is pretty hardcore, I'm impressed that you've started there, but it's pretty complicated (for me anyway, and I've been animating for about 10 years). I started out using (and still use) a program called SwishMax, which you can download a 15 day trial version of. It's to Flash what Paintbrush is to Photoshop, but it's also a really easy way to do decent animations without lots of expertise. Might be a place to start.
Hey. Like the animations you've done. I wanna make some like that!!! However, I'm only 13. I probably wouldn't start making animations until Year 11. What age did you make your first animation? If you don't mind me asking! I managed to make a very jerky moving circle on Flash Mx at school the other day