My adsense earnings are very low for the last three months. Why? my blog is http://learn-free-medical-transcription.blogspot.com
The English is very hard to understand and obviously wasn't written by a native speaker. If you are targeting the US, that would be a problem.
Whats the total age of the site? Have you been changing alot of things around? Like colors, layout, ad position. I noticed my earnings drop when I changed layout on my site. Try also different colors for the ads. Good Luck