For stolen submissions, try to find from where they downloaded your articles and report them. All article sites that offer articles for reprint do so under the creative commons license that only allow reprint with links and content intact. Also, you can email the thief webmaster and demand they remove your content. Unfortunately, there are a lot of losers on the internet that cannot write their own stuff and so they steal others.

I do not write articles for each post, I write general articles relevant to the site and then put my backlinks in accordingly. I generally write at least 6 articles a week per site, the more the better.

Also, are you writing for a blog, or a site? With the blog you get pingbacks and so you know who has used your articles because you get a ping alert for the links back, but with websites you don’t have that, so your articles maybe going viral, but you would have to do an exact search for the title of the article in G to see what sites have reprinted your stuff, so you maybe getting reprinted more than you think.