My title is showing after the shortcode

You needs to change buffer like this:

<?php

    function shortcode_callback() {

        ob_start();

        //my code here

        return ob_get_clean();

    }

    add_shortcode('shortcode', 'shortcode_callback');

    ?>

Please check after replace ob_get_clean(); in your code with return ob_get_clean(); then it’s working fine.