Domain Change Issues

I bought a new domain and changed my old custom domain to the new one (per the suggestion of GoDaddy -- domain was purchased from them). What GoDaddy didn't tell me was that I needed to change the nameserver on GoDaddy prior to making this edit.

So here is the issue -- when I type in the old URL my site comes up, but when I try to login as an Admin, it redirects to the new URL (which doesn't point to anything). Thus, I can't login. I get stuck in a circle of redirects. I try to login from wordpress.com but it doesn't recognize my username and password. It never has -- I've always had to login from my site.

The simple fix would be to use namerserver.wordpress.com, but I haven't used that url in years and can't remember what it was. Is there a way to uncover the hidden domain?

Previous url was: atxjammers.com the new one is jammerslacrosse.com