I am so sorry to hear this news.
My wife and I lost our first child at the age of nine weeks back in '99. The coroner was not able to determine the cause of death, and so I know how frustrating it is not not have a reason to be able to grab on to and wrap your mind around. These are the times that you just leave it to God and carry on the best you can. As our pastor said to us, "Don't be afraid to be angry with God. He can handle it." Anger is just one stage you will pass through, even as this happens so slowly.
You have just the right attitude when you say that it will bring your family closer together. You will need that strength in times to come, and it will be worth it in the end.
And don't be afraid to try again someday when you feel you're ready. We now have a year-and-a-half old daughter who is completely healthy. Every day with Kate reminds me of the brief happiness we had with Nick, and the gifts that each of us give, even unknowingly, even when unborn, to one another.
Everything has a purpose, even if we perceive it not. Hollow words now, but something to keep in mind later.