can't log in anymore

You need to change the urls back to what they were before. Have a look at this page which has detailed instructions for various ways of doing that.

Don’t be put off by how much info that page has. Read the intro paragraphs, and then look specifically at the section I linked you to: Edit functions.php. It’s just a few steps, but be sure to take it step by step.

That page has links about ftp if that’s new to you. If you still aren’t sure how to access the file, ask your web host to help you.

also see:
http://codex.wordpress.org/Settings_General_Screen