I had the same situation. I had two kids, easy conception, easy pregnancies, easy all the way around. When we went for number 3(I was 31), I had two back to back miscarriages (8 wks and 6 wks). I spent two years chasing answers, spending tons at fertility doctors. One lady wanted me injecting steroids twice a day, have IGC (?) transfusions, weekly ultrasounds, a special very restrictive diet.........It ended up all I needed to do was take extra folic acid and a baby asprin. (I chose to go with the least medical intervention and try our luck) We now have an 11 month old!!!
I understand your feelings of defeat. I felt angry and betrayed by my body. It was so easy before. Why couldn't I make this work now? Was I dying? What was wrong with me? Was God or the universe trying to stop me from getting in over my head? Trying to tell me that was more than I could handle? Please know that there is hope for you, and it might not require terrible amounts of drugs or fertility treatments. Hopefully you and your doctor will be able to figure out something that will work for you.
There is absolutely nothing wrong with you wanting to add to your family. People seem to think anyone who wants more than two kids is being "greedy" or "selfish". Most of my friends told me I should just give up and be thankful. I already had a boy and a girl, what more could I possibly want? I also had a friend who said it was clearly a sign that I should never have more kids. Ouch.
You are so completely not alone. I learned after my experiences that so many women have had miscarriages. I would say more than half my mommy friends have been through it. Some went on to have more, some didn't. Statistically, 15% of all pregnancies end in miscarriage.
Best of luck to you. Email me if you want to discuss further. My heart goes out to you.