Miscarriage

When I was 16 (I'm 21 now) I had a miscarriage. At the time I thought it was a horrendous period as I was on the pill (admittedly I wasn't good at taking it). After speaking to a doctor recently and hearing other people's stories of miscarriage I've realised it was a miscarriage. Before this realisation I was fine. However now that I know I can't stop thinking about it. I'm awake for hours some nights just thinking about the possible child I might have now. Does anyone have any tips to overcome this? It almost feels like I'm grieving.