I seem to have lost my username...

I lost my username for signing in and I can't start my server now. I tried to sign in with my email but it says that username doesn't exist. What can I do to find my username? It says I have saved login information for the site but when I try to use it, it says it doesn't exist, and now I can't access my server. (Don't judge the name, my group of friends are weirdos lol https://autismosunited.aternos.me/ ) If someone could figure out how to get a new account that can control this server, or help me get access to my server, that'd be awesome. Thanks!