Hi webmasters,
I know that if we want high pagerank then we can build many backlinks. So I had built so many backlinks.But now they are decreasing day by day instead of increasing. And I am still continue working on building backlinks, but not positive results.
Please help me in this matter.

It takes time and it's normal for there to be some decreasing. As long as you keep building and give it time, there should be a bigger trend of increasing even if it drops sometimes.

It means your links are getting deleted or removed. This happens if you automate your links since the webmaster regards them as spam. Manual link creation is the best.