So sorry to hear that you are going through this pain.
My first pregnancy also ended in a missed miscarriage. I went to my ultrasound at 13 weeks to be told the awful news. I found going back to work really difficult as a work collegue was 4 weeks ahead of what I would have been with my pregnancy. Like you my pregnancy was also the first on both families, we had only told them I was pregnant the day before as the Dr had told me everything was fine, I just wanted the ultrasound to see the bub so I too felt really bad, guilty etc. As others have said be gently with yourself.
You mentioned you don't know when it will hit you, for myself 4 weeks after my D&C I had my first period, I think I had a breakdown at work, it was like the final confirmation for me that I wasn't pregnant, plus I think my hormones were all over the shop a bit too.
It slowly got better after that moment though.