Can't log in with current username

I just downloaded wordpress and created my new website yesterday. I could log in yesterday and everything was fine. Today, when I tried to log in on the mobile app, it said I had the wrong user/pass. The iOS support person told me to try logging in on my computer on a different browser to see if those specific user credentials would work, and they did not.
So I am currently logged in on Firefox, looking at my username, and that same username is “invalid” when I try to log in.

I’m not sure if this could have caused a problem, but yesterday, I deleted my original admin user profile because I thought the username would make the account easier to hack into. I created a new profile with a more secure username, and I DID make sure to give it the title of Administrator. It is this new one that is no longer working for logging in (and the old one doesn’t work either.)

Please please help, this is an extremely frustrating issue. I am reluctant to continue creating content in case something weird happens and it gets lost. My website isn’t active yet, but it is eatlearnlove.net.
Also, I don’t really know anything about being an admin, coding, or any of this stuff… So if this problem has a pretty technical solution, it would really help me if you used as much “plain English” as possible. Sorry, I know that is a bit limiting, but you would be wasting your time answering if I can’t understand you at all.
Thanks!