Normally, you have to wait 12 weeks after the date of your marriage to apply for the certificate.
I mailed my application to "Office of the Registrar General" and waited a long time to get the certificate. So you had better check with local office that how long you have to wait to receive the certificate if you apply in the local office.
Be patient, if you need it urgently, talk to them to see if they can deal with your case soon.