Ask HN: Website not appearing in Google search anymore?

Long time ago I made small adsense niche website howtohavetwins.org Small website, earns like 5$ a month :) It was 3rd search result on first page when you type 'how to have twins' on google.com. But few days ago a noticed that it's gone from google. I checked Google webmaster tools and I didn't receive any warning messages. How can I get my site back on google?

I read somewhere that the reason for dropping from google can be spam on your site? I use wordpress plugin which automatically post content related to any topic of your choice to your site, maybe that's the reason for this?

Thanks for any help.