Update changed my username and deleted my website? HELP!

I am very new to WordPress. I had just finished building my site and not yet backed it up. I saw an update button next to my WordPress… I clicked it. My site was completed wiped out, which reading after the fact I realize I was supposed to back it up. But the more peculiar thing is that my username was changed. “_1ev0rvgl” was added to the end of my username. Is this normal? Can anyone help me? ??