Very simple infinite scroll in WordPress.

home.php

//Just a random file for loading your posts to see that the infinite scroll works. 
<?php get_header(); ?>

<div class="col-md-6 col-md-offset-3">
	<div class="post-container">
		<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
			<div class="page-header post">
				<h1><?php the_title(); ?></h1>
				<p><?php the_excerpt(); ?></p>
			</div>
		<?php endwhile; endif; ?>
	</div>
	<?php
	  //You will probably want to wrap this in a div and hide it from your users. 
		the_posts_pagination( array(
			'mid_size' => 2,
			'prev_text' => __( '<i class="fa fa-angle-double-left"></i>', 'textdomain' ),
			'next_text' => __( '<i class="fa fa-angle-double-right"></i>', 'textdomain' ),
		));
	?>
</div>

<?php get_footer(); ?>

infinite-scroll.js

(function($) {
    $(window).scroll(function() {
        var url = $('.nav-links .next').attr('href');
        if (url && $(window).scrollTop() > $(document).height() - $(window).height() - 150) {
            //To avoid repeating calls we set the paginate container to hold only text and we remove the links.
            //that way url variable would be empty, thus if statement would return false and not continure to the get call.
            $('.navigation').text("Fetching more posts..."); //You can optionally load an icon-loader or something.
            $(".loader").removeClass("hidden"); //Show the loader icon

            $.get(url, function(data) {
                var dom        = $(data);
                var next_posts = dom.find('.posts-container').html();
                var pagination = dom.find('.navigation').html();
                $('.posts-container').append(next_posts);
                $('.navigation').html(pagination); //We want to load the new pagination with new links.
                $(".loader").addClass("hidden"); //Hide the loader icon

            });
        }
    });

})(jQuery);

I did this based on this video - https://www.youtube.com/watch?v=PQX2fgB6y10

this code doesn't work.

@doungancol If it's not working that means the selectors are wrong. It depends which WordPress pagination function you use. Just check and adjust accordingly. If you have problems let me know, but the code works in general.

I removed all the code that handles the back button to avoid confusion since it's not 100% ready yet.