Are your articles original/unique? Do they have your keywords in them? You should optimize your content to whatever words you are trying to get ranked on. If you have a website that sells cars but only use the term "vehicles" in your site then you won't be ranked on "cars". Also, make sure that the anchor text of your backlinks contain your keywords as well
One question for you: Where are the 200 articles? Are they on your site or did you go to 200 different sites and add the articles to them? How many different arrticle sites did you post to? Adding articles only to your site help some of the SEO, but having 50 different article sites pointing to your site will add more to your SERP results.