I have had a Google page 1 ranking (position 3 through 5) for about 5 months prior to the middle of October 2013. For two months before that, I was unable to backlink to my website. Around October 15, 2013, I checked my SERP listing in Google, and it dropped to page 3. Prior to that, my ranking had been quite stable. There were no on-page changes prior to the drop. Since the drop, I have been linking for about a month, but I am having difficulty getting back onto page two.
I would expect some sort of gradual or incremental drop in rankings due to the lack of my backlinking activities, but not such a sudden drop.
Did the drop in ranking come about because my backlinking activities had stopped, or has there been a change in the Google algorithm?