What shall I say to my doctor?

Ive heard that if you are trying to get pregnant you should contact your doctor and speak to them about the best ways to conceive. I want to do this as in concerned about my fertility. At my doctors you have to ring the reception to book an appointment but you have to say what is wrong with you and why you need to see your doctor, I was just wondering what I say over the phone? I'm a little nervous about doing this as I have neve really needed to before