I had a mmc at 13 weeks before DS1 with no bleeding whatsoever. So, to be honest I was worrying pretty constantly anyway in the early stages of this pregnancy. I had a scan at what I thought was 6+5, turned out my dates were out and I was more like 5+2, so there was no heartbeat, barely even a dot of an embryo. I had to wait 2 weeks for another scan, which showed a baby with a heartbeat, and from then to 14 weeks I had a scan every 2 weeks. The bleeding at 16 weeks was so heavy and I was cramping, so was convinced I was miscarrying, but everything was thankfully OK with the baby. So, I guess I've had a pretty constant feeling of panic and worry since I did the pg test! Like you I just kept thinking, if this is going to go wrong, please just let it happen now.
At the moment to be honest I'm not really thinking about the due date too much. It seems so cruel that it's the exact same date. But, what with the subchorionic haematoma, and the fact that my placenta is currently very low, I'm not sure I'll make it the full 40 weeks, or at least that's kind of what I'm hoping. I'm literally just trying to take each week at a time at the moment, as it seems like the only way to cope. I can't plan my maternity leave, I can't think about my DS3 being born, can't bring myself to decorate the room or anything, as I don't want my heart to be broken again. One of the worst things is trying to explain it all to DS1 (2.8). He thinks he's going to meet DS2, and really doesn't understand it all at the moment.
I feel happy about this pregnancy in that I feel happy I conceived again, happy that I'm on the path to having a baby again. But, I'm terrified of it all going wrong again, so in a way I don't really "believe" in this pregnancy if that makes sense. And as for coping with the loss of DS2, I'm not sure I have/do. I just try and slowly move forward in the hope that it might make the pain more bearable.