Here are some ways you can find out who shared your link on Facebook.
The method that I personally use to find out who has been sharing links to posts on Techlivewire.com is to use Google itself. Google search alone can do a lot of things that you never knew it could. Here is a custom search query that narrows down links shared on Facebook to my site. The query I use is “https://techlivewire.com site:facebook.com” or you can also try “links:techlivewire.com” which shows you all links on the web referring to your site (don’t forget to replace techlivewire.com with your own website). This query shows me all links on Facebook that link to my site. It even shows me links I myself have shared on my official Facebook page for my site. This query is very useful and more dependable than sharedcount.com method below.
http://sharedcount.com works, just make sure to try both with and without the trailing slash in your link.
This is one of the limitations of Facebook. You can’t get an accurate picture of who has shared your content, unlike twitter. Facebook should introduce something like an internal search (which Twitter does) without compromising on user’s privacy somehow.
Another way you can tell who shared any link of yours on Facebook, is to check your Google Analytics or whatever visitor stats you use. It should be able to show you Referrer links. So if you see a referred visit coming from Facebook, then you can bet that is a shared link. You can do further digging to see exactly what link that Referred visitors went to on your site.