Featured Image Fallback and remove first image in post.

I am having issues with my code for featured posts. Here what it does:

1. If has featured image > Show
2. If doesnt > Show first image in post (also need to delete first image in post)
3. If no image in post and no featured image > default.jpg

What i need is to delete the first image in the post so it does not repeat (#2). I dont know where to start any help

Here is the code:

function get_fbimage() {
  if ((function_exists('has_post_thumbnail')) && (has_post_thumbnail())) {
  $src = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), '', '' );
  $fbimage = $src[0];
  } else {
    global $post, $posts;
    $fbimage = '';
    $output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i',
    $post->post_content, $matches);
    $fbimage = $matches [1] [0];
  }
  if(empty($fbimage)) {

    $fbimage = "https://www.example.com/defualt.jpg";
  }
  return $fbimage;
}