You don't need to use your SSL certificate for the CDN. Most websites that use CDNs only do so for static assets such as images, fonts, CSS, etc... the dynamic content comes from the origin server, encrypted with a private key that is not handed out.
If you press F12 in your browser and navigate to some major sites, you'll notice anywhere between 1-5 different CDN domain names that aren't directly related to the original host in any way.
If you press F12 in your browser and navigate to some major sites, you'll notice anywhere between 1-5 different CDN domain names that aren't directly related to the original host in any way.