Hey Dan...You're right, I've heard that an itchy anus one of the signs that you might have parasites...unfortunately I have one too, sometimes! (can't believe I said that for all to see...my my...)
Anyway, if I were you, I'd go another round of parasite cleansing (just keep on it) People here have had great luck with CoQ10 (or whatever it's called) just scroll down and search for posts about that, there are plenty...you might want to try that as well. And, while you're continuing your parasite cleanse I think it would be most beneficial for you to do a liver flush. People get out the craziest things (besides stones) when parasite cleansing and liver flushing.
That's what I'd do. Read all you can! You're doing the right thing...