How to know if someone is copying your site content?

Last Friday while doing my project. I got interest to check why **** company website is not searchable on the search engine. I found out it has a “100% duplicate content”. Meaning, this www.siteA.com and www.siteB.com is 100% the same look and feel and contents! Then it cross in my mind if I also have a duplicate content? Or is someone stealing my personality? Happy to say… someone copied my content. 10-15% of my content on this page is copied by others. Why I am positive about it? Because if someone is copying you… meaning your style is working.

Btw this link  www.copyscape.com helps me to track my dopple ganger!  ;)