Previously I check my backlinks on Google is 25 but wonder why, now fallen so much that I have to link it unchanged http://www.google.com/search?q=check...9c50a61d5b9175
Where or HOW are you checking your links on Google? If it is with the link operator then you really have no idea if they are really there. See: http://forums.digitalpoint.com/showthread.php?t=1932187
SEO Spyglass is a very nice free tool that you can use but if you can not afford to download and install the program on your computer then you can simply use the Yahoo Site Explorer.
Spyall is the best free SEO tool used for tracing backlinks. I always use it and it gives me accurate results.