Solution:
I have this issue too,
backup your .htaccess file, and use this
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
then, in wp-config remove the https back to http
define('WP_HOME','http://www.example.com');
define('WP_SITEURL','http://www.example.com');
this should get you back to the dashboard, and you can start working on it again.