Congratulations on making your CAPTCHA almost unreadable to humans, let alone robots. If your aim is to drive away the users of this site, then you are well on your way to achieving this goal :-(
Really, it's the worst CAPTCHA I've ever seen, anywhere, period. I had to guess at half of the letters/numbers (of which there are quite a few), such that I'm really amazed that I actually managed to log in at all (after some attempts). And I might simply not bother trying next time.
If you have to resort to making it that illegible, then I have a tip for you: Spammers are not using computers running super-complex algorithms to break your CAPTCHA, they are using a far cheaper resource: Underpaid (or possibly even free) human beings.
There are very poorly paid people in China/etc whose sole job is to 'solve' hundreds of CAPTCHA per hour. Although if I was a spammer, I'd get it done for free by setting-up an illegal site (offering movies or porn or whatever) and requiring that people solve a CAPTCHA to download something (without them realising they are actually solving the CAPTCHA from a legitimate site such as yours).
Rant over! Feel free to ignore my moaning, but I think you risk driving people to other sites. :-(