Please provide all of the information requested below in a support ticket.
1. The domain in question. It would also be helpful to know who your hosting provider is and if you are on a shared or dedicated server.
2. What you are using to test. If you are using a report from an online reporting tool, for example, please provide us with the URL linking to the report.
3. Where the slowness is specifically on the site. If you are seeing it on dynamic content, which we do not cache by default, then the issue is most likely with your webserver and you should contact your hosting provider.
4. A traceroute to your domain so we can see which CloudFlare datacenter you are hitting. Directions for a traceroute can be found here: https://support.cloudflare.com/entries/22050846-how-do-i-run-a-traceroute
5. The output of yourdomain.com/cdn-cgi/trace (replace yourdomain.com with your actual site name).
6. If you have made any changes to your site recently, including turning CloudFlare features on or off in your settings.
Important: Please check to make sure that requests from CloudFlare's IPs are being accepted by your server. Performance issues and other problems can occur when our IPs are either being blocked or rate limited.