Can I view my ssl FQDN? How do I fix the mismatch

I have probably set wrong FQDN while creating ssl certificate.

Now, certificate is installed and site display a ‘Warning: Potential Security Risk Ahead’

I am quite sure it is FQDN as certificate was bought from a company where i have installed ssl successfully in the past.

I get this detail on the site:

-when visiting https: www.mydomain.com: Web sites prove their identity via 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 not trusted because it is self-signed.

How can I view ssl FQDN and how to fix the issue.