If you are asking a question, try providing enough information like the address of your blog, how old it is, the number of backlinks it has, etc.
That's how google works, every 5 minutes or so, SERP could give you a different rankings from time to time. Probably you're site competition beat you into the rankings, you just recently made a big major update on your site or somehow google penalyzed your blog(hope not though). If you're link building strategy worked before giving you results, just continue on doing it, you may have just experienced a google dance. What's google dance? check this out http://www.google-dance-tool.com/what_is_google_dance.html
yep.. it's google dance. if your site is new, give google at least 3 weeks for your website to get indexed
one of my site is the same, getting lower ranking compare before. SERP is updating for the keyword, dance is taking place.