Moving on after miscarriage

I have two beautiful kids and had decided that two was my number, I was finished.
However I fell pregnant again, I was scared and overwhelmed at the thought of coping with 3 young kids not to mention how we would afford things.
I had started planning and getting my head around it all when I had a miscarriage.
I was heartbroken, I hadn't wanted another baby but it was still mine.
My question is how do I get over this? How do I stop thinking about my due date and how I would be ....weeks pregnant now. Seeing babies and thinking I could have had another one of those?
I still don't want more kids but just don't seem to be able to move on, it's been 6 months now and I thought it would be getting easier.