I have 1 site. http://www.exmbt.com I used to add back links for about 2 monthes. the back links of the site is creasing to about 4600 or more. But these days, I found that it was decreasing . The back links is getting reducing. What happened. We are always doing back links building work.
As u said that your back links are decreasing, that may be due to some links on the spam/fake sites and Google would have devalued those links. So try to get back links from some trusted websites. Or you might be over doing it big time! First do some analysis and research then proceed.....
some of the sites that linked to your sites may have gone down or out of business or something like that. Also if you got links from blogs or news sites these older posts that linked to your site might just get naturally deleted over time by the owners of the site.
Building backlinks using 99.9 percent of the services offered in BST will have this effect. In a nutshell build relevant, in content links or what you do only works for a short period of time. Nigel