CCF Copyright Rules ... Can I Use My Own Contributions?

Heck no, have at it!

I'm not a lawyer, and free advice on the internet is worth what you paid for it. But...

Unless there's something in the CCF terms that we agreed to when we joined, and I don't recall anything like that, you as the original author retain your copyright. You can reuse, republish or even release to the public domain at your own choice.

At most CCF has a compilation copyright, which would mean you couldn't republish the entire body of all author's works or even a substantial piece of it. But in classical copyright law that's even questionable since there's no 'sweat of the brow' required in the compilation here. One of the classic cases in that area involves sports statistics - the statistics themselves as facts are not copyrightable. But the specific selection of facts represented and the organization, presentation & design of the presentation is copyrightable.