Have I just lost everything?

So I just finished on my wordpress site. I had a guy do some coding and I edited the content etc. It took around 2 weeks. Now, I went to change the domain which was another hosted domain from the guy who was coding, so it was not example.wordpress.com Anyways I bought a domain from godaddy, changed the nameservers and then I went to the setting pages on wordpress and changed the URL and site domain to my godaddy domain that I bought. I did not go to the Store settings or anything like that. Literally just done it from my admin setting I believe. I literally just changed them on the setting page. Immediately after I hit update I was faced with a “cannot find the page you were looking for” bullshit. Now I cant access the site or even log in. Have I just lost all my coding and content material? Does anyone know what happened or why? I’m literally freaking out right now!!