how can i find out why im dropping in google ranking on different keywords, every day i check i loose some of rank.

Rankings go up, rankings go down

stop checking them.

How's the traffic and conversions?

rankings keeps on changing...you should keep in mind that SEO is a continuous process and that your competitors are doing everything for them to outrank you...

also keep yourself updated with new trends in SEO, try also to study your competitor's changes!

Chris is right, Look at only traffic and conversions. In reality there is little difference between ranking first and 5th, If your result accurately reflects what the searcher wants they will click it.

Obsessing over rankings by searching your keywords on a daily basis is a completely unproductive use of your time.

In addition to what Chris and st0x said, rankings will vary across datacenters and even across servers in the same datacenter. So what you see will probably not be what I see will probably not be what Bob sees will probably not be what Sally sees.

The only thing you can check to determine how well you're doing is your site stats. Are you being found more often (by everyone other than you)? Are you being found under more keywords? Are you attracting more traffic? Are you converting more?

These are the questions you need to ask yourself.

A lot of links are getting discounted latley as well. Stay away from footer "site-wide" links....

try to gain good quality backlinks with can result a good keyword position instead of thinking of your dropping keywords.

If you are standing still then you are moving backwards in the seo world.

Ranking keeps on changing, don't worry concentrate on SEO and keep an eye on what your competitor is doing for getting better ranking and try to overtake him....
Be in touch with SEO practices...

Ranking Dont Matter, if you get traffic and sales that is all that matters. Their are other means then SEO to get visitors and lots of them.

Just continue to build more quality links for your site.

In SEO world nothing is constant. the only thing that is permanent is that you have to continuosly optimize your site

continuous getting of "related" backlinks, putting fresh contents and updating your sites regularly can help you back on track...

basically you need to do more seo work. get more link to your site with good anchor text. and write more new content to your site weekly.