Category Foreach keeps looping?

I’m using the following code to acquire all the child categories of a category and displaying the child posts of the child categories.

<?php
$cats = get_categories( 'child_of='.get_query_var( 'cat' ) );

foreach ( $cats as $cat ) :

    $args = array(
        'posts_per_page' => 3, // max number of post per category
        'category__in'   => array( $cat->term_id )
    );
    $my_query = new WP_Query( $args ); 

    if ( $my_query->have_posts() ) :
        echo '<h3>'.$cat->name.'</h3>';
        ?>

        <?php while( $my_query->have_posts() ) : $my_query->the_post(); ?>
            <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
            <br />  
        <?php endwhile; ?>

    <?php else : ?>
        No Posts for <?php echo $cat->name; ?>
    <?php endif; ?>
<?php endforeach; ?>

and i want to acquire this output.

 Cat Child 1
 -Post1 Child 1
 -Post2 Child 1
 -Post3 Child 1
 -So on... .

 Cat Child 2
 -Post1 Child 2
 -Post2 Child 2
 -Post3 Child 2
 -So on... .

But instead of that, both the child categories are being repeated over and overagain. Can anybody tell me what the problem is? This is the output I have now.

 Cat Child 1
 -Post1 Child 1
 -Post2 Child 1
 -Post3 Child 1
 -So on... .

 Cat Child 2
 -Post1 Child 2
 -Post2 Child 2
 -Post3 Child 2
 -So on... .
 Cat Child 1
 -Post1 Child 1
 -Post2 Child 1
 -Post3 Child 1
 -So on... .

 Cat Child 2
 -Post1 Child 2
 -Post2 Child 2
 -Post3 Child 2
 -So on... .
 Cat Child 1
 -Post1 Child 1
 -Post2 Child 1
 -Post3 Child 1
 -So on... .

 Cat Child 2
 -Post1 Child 2
 -Post2 Child 2
 -Post3 Child 2
 -So on... .

until it loops 9 times and stops. what is the problem?