sites merged after install, help!

I guess the best way to explain this is to go step by step:

1) I have a website/blog that had just been successfully moved to WP from Typepad, hosted on dreamhost

2) bought a new (second, separate) domain for a small professional site

3) my boyfriend installed WP to the new site via some one-click thing thru dreamhost. He says he DEFINITELY installed on the new site and not the old one.

4) I went to (sitename).com/wp-login and completed the install (I thought that was the right thing to do) and in that process used the same login info as my other, aforementioned blog site. I’m thinking this is where I went wrong but I thought the system either wouldn’t let me do this if I couldn’t or the fact that it was a totally different URL would make it ok.

5) I was tinkering with it, the control panel was totally different, none of my other themes were there (still aren’t) chose and DL a new theme, started working on it, then an hour or so later I tried to navigate to my original site and it has now become the new site, all my old content is gone.

I have no idea what happened, how it happened, or what to do. I’m trying not to panic, and I do have my old posts still on TypePad, but I just had them all moved over! Please help!