Content Filter causing double posts

For some reason this is causing my post content to show twice, as well as the “testing content filter” part.

It works fine on another site, I’m using it to display adsense at the bottom of each post, but I can’t get it to work in my 2011 child theme.

Anyone see anything wrong with it?

/* Filter the_content() */
add_filter( 'the_content', 'my_content_filter' );
	function my_content_filter( $content ) {
	   if ( is_single() || is_page() ) {
		  $content .= ' ***TESTING CONTENT FILTER******* ';
	   }
	   return $content;
	}

EDIT: nvm, was a bad copy and past in my single page template >.<