J., First and foremost, there are NO right words to say in a situation like this, but I am very sorry for your loss and my prayers are with you. So, here's a different perspective on handling miscarriages, and I do apologize if I come off too strong as I am a blunt person.
Sooner or later you will get over this, no doubt. It does NOT seem like it now, but I promise you, you will survive it eventhough it is the end of the world now. You are already a lot stronger parent/woman than the rest, because you have a special needs child.
Miscarriages are more common than you think, people just don't talk about it a lot. I tried to get pregnant for years (naturally, no IVFs, etc.), and kept having several miscarriages, I became "immune" to them for lack of better word. Miscarriages can be equally physically and emotionally painful.
I've been through it all.... Pills, shots, d&c, scraping, natural passing, you name it I've had it. With each loss, it only made me a stronger person. Because I believed, one day I will have a baby and God will answer my prayers, and 8 years later, I have 2 wonderful children. I also have scars, stretch marks, loose skin, or any other ugliness you can think of, but I am a mother, and loving it. So, believe it or not, I will not change anything about my life then or now. Whatever happened to me, needed to happen to make me a better and stronger person I am today.
Also, ina different perspective, stillbirth scares the $hit out of me and is something I find absolutely soul shatterring. To bury a child right after the birth...been blessed enough not to have the xperience, but not sure how I'd handle something like that .
Pain of miscarriage is different if you're going through it for the first time. I listen to music a lot. Whether it's a happy or sad song, it ususally helps me cope better with whatever life throws at me.
Please take time to grieve, name the baby, buy a charm bracelet, whatever else it takes, but don't forget life goes on and time heals. You are not alone in this and there is definitely life after the miscarriage. Remember my words about a year from now.