SSL Certificate – Can I View my SSL FQDN? How do I resolve the mismatch?

I probably set a wrong FQDN when creating the SSL certificate.

Now the certificate is installed and the site displays a warning: Possible security risk in advance

I am pretty sure that this is a fully qualified domain name because the certificate was purchased from a company that I have successfully installed SSL in the past.

I get this detail on the page:

-When visiting https: www.mydomain.com:
Websites prove their identity through certificates. Firefox does not trust this site because it uses a certificate that is not valid for www.mydomain.com. The certificate is only valid for mydomain.com.

-When visiting https mydomain.com:

mydomain.com uses an invalid security certificate. The certificate is untrusted because it is self-signed.

How can I display ssl FQDN and how can I fix the problem?