I didn't want my current username. I didn't change it and I am confused.

It used to be toast67

I want it back lol

Go to settings. Username tab. Change it there. 99% certain though that there's no way for it to change besides that.

It says I can't change it

Don't see how it's possible for it to have changed without you (or I guess someone else logged into your account) changing it, but anyway, only the admins can change usernames, so send an email to support@speedrun.com and maybe they'll change it back for you.

Also, pro tip, you can edit your forum posts instead of clogging up your own thread by making three posts in a row.