404 errors

Hi. I keep getting 404 errors from google. For some reason and I dont know how but every link ends with "/url" so I guess that my wordpress creates duplicate of every post and page with "url at the end and google webmaster defines is as 404 and it is a 404 as that pages and posts dont exist.
So for example I create a post. That post url is mywebsite.com/category/postname
but on google webmaster i see 404 errors on every post or page and the url is like this
mywebsite.com/category/postname/url…
404 errors

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