It could be, and these words were used by my dr., a "fanny fungus". A while back after a bad bout of D and possibly a hemmy, I got very itchy there and it didn't go away. Not to worry...a simple application of an ointment twice a day got rid of it quickly.
I would talk to your GI and have him look. It could be nothing more than a rash. Don't get worked up just yet. Feel better.
I know fanny is a butt....hence the fanny fungus. I think in Ireland, fanny means something else though.
This all got me thinking...and I remembered an old South Park episode where a gerbal got stuck into Mr. Slave. (Only SP fans will know what I am talking about probably). Needless to say, I was thinking how the scratching would feel so good on all that itchness.