Display wordpress loop in two columns using bootstrap grid

Hi I need to modify my WP theme to make it show one post in two columns. like this :

but when I add a second post it gets like this :

This is current code of the blog section custom php file, I can do a wipeout and forget this code and start from scratch, i've tried but I cannot make it work... Really appreciate any hint/ suggestion...I'm not a specialist, i'm learning

<div class="container content">
        <div class="row blog-page">
            <div class="col-md-9 md-margin-bottom-40">
                <!--Blog Post-->    
                    <div class="row blog blog-medium margin-bottom-40">
                            <?php // Display blog posts on any page @ http://m0n.co/l
                                        $category_id = get_cat_ID('Blog');
                                        $catquery = new WP_Query( 'cat=' .$category_id. '&posts_per_page=5' . '&paged='.$paged );
                                        while ($catquery->have_posts()) : $catquery->the_post(); ?>
                            <div class="col-md-5">
                            <?php 
                                    the_post_thumbnail('medium') ;
                                ?>
                            </div>
                            <div class="col-md-7">

                                <h2><a href="<?php the_permalink(); ?>" title="Read more"><?php the_title(); ?></a></h2>
                                <?php the_excerpt(); 
                                ?>

                                <?php endwhile; ?>
                                <?php if ($paged > 1) { ?>

                                    <nav id="nav-posts">
                                        <div class="prev"><?php next_posts_link('&laquo; Previous Posts'); ?></div>
                                        <div class="next"><?php previous_posts_link('Newer Posts &raquo;'); ?></div>
                                    </nav>

                                    <?php } else { ?>

                                    <nav id="nav-posts">
                                        <div class="prev"><?php next_posts_link('&laquo; Previous Posts'); ?></div>
                                    </nav>

                                    <?php } ?>

                                    <?php wp_reset_postdata(); ?>               

                            </div>

                   </div>
                   <hr class="margin-bottom-40">
                <!--End Blog Post-->


                <!--End Blog Post-->

            </div>

            <!-- Right Sidebar -->
            <?php get_sidebar() ; ?>
            <!-- End Right Sidebar -->
        </div><!--/row-->
    </div><!--/container-->

thank you in advance for your help