As far as Google changing their algorythm goes its quite likely. Google change their algorythms quite frequently. I have seen teh ranking of my websites for keywords go up and down a lot. SOmetimes by a good few pages. Over the last month I have seen my ranking for keywords such Estate agent web designa nd mortgage web design go to top 5 from page 2. However my rank for my most improtant keyword web design company has refused to come to page 1. It did manage to come to page 1 briefly but has slipped back to page 3 or 4 in the last week. As far as anchor text in links go , i doubt that it has become less important for Google. Anchor text in links continues to be an important factor and you should not disregard it in any case. Not just yet atleast unless it becomes common knowledge. With regards to the fall in rank for your website, I am positive paid links have something to do with it.
It is common knowledge that Google update thier list of paid link websites regularly and do penalise websites that advertize on such websites. My advice to you would be to over a period of time move your links to unpaid websites. It may take time but is well worth it in the long run. Google is here to stay and no matter how long it takes to get yor generic ranking up; it will pay in the end.

I think this guy have fake problem and trying to do spam here...

Well, if you are serious in your question, all you need to do is to continue getting backlinks. Backlinks is the major factor in serp ranking.

Why using any tool to check your site position in search engines..try to do it manually and then you can get more good analysis..

Online tools mostly gives wrong information as search engines changes their algo frequently...

Put fresh content and try to get more and more relevant BLs from related sites...and you will gain positions.