I am so sorry that this has happeneed to you, but please don't lose hope. I don't have advice from personal experience, but, my sister in law has just had a beautiful healthy baby after four m/c and a baby born sleeping at 22 weeks.
Let yoursleves grieve and then see a specialist who may be able to give you some answers, make sure you always get a second opinion if you are not satisfied with the answers or advice you are given.
In my SIL's case she had a blood clotting disorder that was one of the causes of her miscarriages, there are some causes that can be fixed and monitored if the doctors know what is wrong.

My heart goes out to you.....