Jan Dembowski on "HTTPS loop"

Is this the plugin you mean?

https://wordpress.org/plugins/wordpress-https/

If so try these steps to get back in.

1. Using FTP or whatever file management tools your host has provided you with navigate to the wp-content/plugins directory.
2. Once there locate and delete the wordpress-https directory. Just that one directory and nothing else.
3. Try and re-login to your WordPress dashboard.

You may also need to rename your .htaccess file to .htaccess-old (don't delete it) to get back in.