category post per page

im using this code for post per page

add_filter('pre_get_posts', 'limit_category_posts');
function limit_category_posts($query){
    if ($query->is_category) {
        $query->set('posts_per_page', 5);
    }
    return $query;
}

but it makes foreach in the header.php also to be 5 post per page.
the foreach is like this :

<?php $catPost = get_posts(array('category'=>get_cat_ID( 'news' ),'numberposts'=>2)); ?>
<?php foreach ($catPost as $post) : setup_postdata($post); ?>
<div>
content of post in the header
</div>
<?php endforeach; ?>

what can ido?
i want to posts in the header will be only 2 and every page in the category will be 5..

hope you will understand.