This question already has an answer here:
I have a new blog that is 2 months old. In the first few weeks, it was getting indexed nicely and my GoogleWebmaster reports were showing that it was getting crawled and began ranking for some terms.
Then as I kept writing, the GoogleWebmaster report thinned out and showed less and less terms that this blog ranks for. Now there are only 4 terms with one of them being my name.
Is there something I need to do to keep the old posts to remain indexed and crawled?