This happened to me; I forgot my exact username because I'm used to it having a space in the middle or my password was a bit unusual or whatever, and when I couldn't log in, I didn't get an option to send a reminder to my email address, which is a feature most sites have.
As it happens, I had to make a new account to get in (which suits me just fine, because I wanted a username change anyway!).
As it happens, I had to make a new account to get in (which suits me just fine, because I wanted a username change anyway!).