Steph I am so, so sorry about your baby girl. I lost my first baby at 40 weeks and it is a horrible, life changing event. My daughter would have been 25 in February. We had a Post Mortem done and nothing really came up. My placenta was failing and the cord was round her neck and kinked but we could see that at the time of birth. I really don't remember how long the PM results took to come through, sorry.
I had a vaginal birth, so my experience will differ from yours. I was ready to try again very quickly, as you say not to replace your daughter but to have the family that you thought you would have. Emotionally I was told six months but I felt ready before then. I attended several SANDS meetings which I found very helpful and also as (bad) luck would have it I reconnected with two classmates who also lost their first baby within weeks of me so we supported each other.
There is no right or wrong in your situation, you go at the pace you feel comfortable with. In my case I was pregnant quickly and my 2nd baby was due around the 1st birthday of my first baby. I discussed this with my consultant and he agreed to induce me at 37 weeks. I think he would have induced me early anyway but that made a huge difference to me. My beautiful second daughter was born 3 weeks before her big sisters first birthday.
My son was born one week after my first daughters 2nd birthday. They both know about their big sister and we visit her resting place fairly often.
Right now I think I know what you are feeling, I had a big hole in my chest, a feeling that things will never get better and a feeling of 'failure'.
You are in the very earliest days of a traumatic time. When your body is ready and when your mind is ready you will have another baby. The new baby will never replace your first baby, it will just be another baby that you will love just like you love the baby you lost.
I hope I have not been clumsy in what I have said. I articulate this feeling better face to face. 25 years later I still have a cry for the baby I lost, I still wonder what she would have been, I still hate the day she died but time does heal and having more children was the best thing for me.
Steph, you have my deepest sympathies and I hope you can see forward during this sad time 