Why does the page/post ID keep growing when i refresh the post-new.php file?

This is normal behaviour, as I understand it.

When you load the page post-new.php, you run this function:

$post = get_default_post_to_edit( $post_type, true );

where the second argument stands for $create_in_db. If true then this part is executed:

if ( $create_in_db ) {
            $post_id = wp_insert_post(...);
}

inside get_default_post_to_edit().