Did you ever write any stories on AFF, and remember the title? You could search for it, then it links to your profile, and you'll know.
Or if you remember subscribing to a specific story, you could look thought that story's subscribers, and look for a name that rings a bell.
Or if you commented on a story, same thing; look through the comments until you find a name that you recognize.
If nothing else works, and you're all out of options, here's AFF's creater's Twitter page
www.twitter.com/asianfanfics
if you tweet your problem to him, he'll usually be able to help you out.