can't access/create iCloud address

I'm trying to add "Notes" to my iCloud account. It says I need to create and iClould email address to do this. I thought I had created such an address about a year ago. But, it doesn't give me an option to sign in. It just says that I need to create a new address. When I try to put in my address under the "create the email address", it says that this address has already been taken. I have a very unusual name, so I know that this address is not someone elses.