Dear jkb, I'm so so so very sorry to read your sad story. Please know that my thoughts are with you and your husband as you go through the next few months.
My son (first pregnancy) was stillborn* at 19 weeks, on 2 September, nearly three months ago. I had no pregnancy problems, apart from severe vomiting that let up only a couple of weeks before the birth, and all parameters were normal just a couple of days before the birth. I just started to have contractions in the night (concentrated in the lower back so that I didn't realize what was happening and thought it was a pinched nerve that could be dealt with in the morning) and after 8 hours of those, the water broke at 6 am. No heartbeat could be found after that. I gave birth naturally, as I was fully dilated when I reached the hospital. No D&C was done (for some of the same reasons your doctors gave) and I bled for around ten days afterwards. After the birth, a large number of tests were run but none of them showed anything out of the ordinary. There have been no answers at all. The upshot is that I went home the day after the birth, with nothing physically wrong except extreme shock and grief, and consumed by the question "why."
I am thinking back to those first couple of weeks after the birth and the only thing I can say is, make sure that people you love you are around, whether physically or on the phone or through the internet. You need that love right now. The crying jags will continue for a while yet. You will feel very, very sad, very, very angry, and very, very cheated and bitter for quite a long time. Please take all the support you can possibly get. My husband has been a rock for the greater part, though he is on a different grief timeline than I am; hold on to your partner and understand that he will feel differently from you but he is also feeling grief, just in his own way. Some of my friends have been wonderful. I found a good counsellor too. And it was very important to talk to my doctors (sadly, the doctors who looked after me for the first trimester were not around when this happened, as I was on a visit to my parents in another city).
The best advice my doctor gave me was that I had to concentrate on looking after myself first and not think about future pregnancies. Daily exercise, healthy eating, and anything that would help me control or vent out my emotions. This is still helping. Going back to something as close to my pre-pregnancy routine as possible was also very helpful. It hurt horribly to do the same things again, given that life was suddenly so different, but it did make things more manageable and gave my life some much-needed structure.
I also obsessively read material on the internet in the hope of finding an answer. Perhaps the constructive way to do this is to allow yourself to do it for a limited amount of time each day or for a limited amount of time once every few days. It's a form of trying to understand and rationalize what happened. I have still not found any answers and have had to step away from the computer to avoid being wrung out by stories of people who had repeated losses at that stage. It's hard. No question about that. We put a lot of faith in medicine and science and tend to take pregnancy and birth for granted nowadays. But there are still risks involved, that's what we've learned.
Good luck and my sympathies -- no, my empathy. I KNOW what this feels like. As time passes, it will feel less raw, but you have to do your best to just pass that time.
Please inbox me if you'd like to talk more.