Are you affected? Yes, probably.
Should you be worried? Probably not. Chances are low that it's actively been exploited. There is some residual data around, but chances are good that you'll be fine.
Should you change your passwords? Yes, probably. But you should rotate your passwords regularly anyway.
Am I downplaying the threat? Absolutely - Cloudbleed is REALLY, REALLY BAD. But it probably won't affect you. It's potentially worse than heartbleed and heartbleed was already really bad.
What is Cloudflare? Cloudflare is a service that sits between a website and you, making it so that you get data from a location closer to you than the website actually is. My websites are in Oregon, Cloudflare means that, from Australia, you only have to get to Sydney to get my site.
What happened? They had a memory leak. I could send a certain command and get a page full of garbage. Sometimes, very rarely (specifically 0.00003%), that garbage will have something interesting in it. However I can send that command as many times as I like.
What is a memory leak? Say I tell you to read 13 words of page 197 of the Lord of the Rings, but you misheard me and read 13 billion words. That's more words than the book contains, so you're just reading everything you can find.