I am so very sorry for your loss.
I don't have a whole lot of info, but I am happy to share what I was told when I lost our little one back in September:
There are many reasons why we m/c, and most of them are out of our control. My obgyn told me that in the early weeks, a m/c is usually a chromozomal thing and is not due to anything that we, as mothers or fathers, do wrong. She said unfortunately, those pregnancies are usually doomed from the very beginning, because when the sperm and egg met, all the many things that have to go right, simply don't, and it only takes one thing going wrong for the pregnancy not to work out.
If I had had a D&C, I could have opted for testing to be done on the fetus that can usually give some more specific answers, but as this was my first, I chose for a natural miscarriage and did not really want to know why.
Here in the states, they usually will not have you and your significant other go under further testing until you have three m/c, and that usually gives a lot more answers, but it is heartbreaking to have to go through that many losses before getting that info.
Take care