Now at this moment contact your hosting provider to help you issue the SSL certificate.
You need SSL certificate on the origin host and then change the SSL at Cloudflare dashboard.
If not, then you have to re-configure your WordPress related settings and use some kind of a plugin which would serve and handle HTTP to HTTPS such as Really Simple SSL on the server side, while keeping Flexible SSL option active.
If you don’t fix this, you’d have insecure setup and mixed content errors followed by redirection loops as well.