Lost my Admin screens, WordPress stuff

I also lost my ability to log in!! I need help desperately. I was logged in as Admin to make some changes and was just finally going to “go live”. I don’t really know how to go live so was trying some things and this is where I screwed up. I went into Settings/General and removed the “wptest” from the end of the WordPress Address URL and Site Address URL. When I clicked the button to save, I got a 404 screen. I clicked the back button and put these back in but have never been able to recover. I do get a log in screen but it looks completely different and doesn’t let me in. And I do know my password. How can I get back to fix this?