Here’s a response I once received from support:
Thanks for contacting Cloudflare support. My name is Damian and I will be looking into this ticket for you.
I can see you are on a partial setup through a hosting partner (BlueHost) with us.
A partial setup means that you do not use our Cloudflare nameservers and instead use a third-party set of nameservers and then proxy through us with CNAME records. The other method of setting up Cloudflare is called a ‘Full’ setup where you move to Cloudflare’s nameservers for your zone. These methods are discussed below.
What are the partner Cloudflare Full vs Partial/CNAME setup?
If you want to use Cloudflare’s nameservers, you first need to delete your zone from being integrated with BlueHost – In order to delete/deactivate the zone from Cloudflare, you can login to our dashboard and click on the ‘Advanced’ link from the Overview tab and click on the ‘Delete’ button.
Once you have deleted the zone you can add your domain following this guide – Getting Started withCloudflare
and we will give you the nameservers once you reach the ‘pending nameserver update’ stage.