What Causes Delay In Periods Post Miscarriage?

I have not had my period or ovulated since my very early miscarriage 8 weeks ago. I saw my GP today who said I just had to wait for my period to start naturally. He questioned whether I d experienced a very early miscarriage at all as the pregnancy test I did at the hospital was negative (where I was diagnosed with a vem at the time), however even though I have been trying for a year he refused to refer me for fertility tests as he said I had obviously conceived. How can I start my period so I am able to start trying again?