Try to use wp_update_post()
in place of wp_insert_post
for update.
$id = wp_exist_post_by_title($post['post_title']);
if($id !== false)
{
$post['ID'] = $id["0"];
// Create Post
$post_id = wp_update_post( $post );
} else {
$post_id = wp_insert_post( $post );
}