I am very sorry to hear your story. If it helps to hear - my cousin's wife miscarried at around 13 weeks a baby with downs syndrome at 29 and went on the following year to have a very adorable and very healthy and happy baby. Since that time she has also had a second healthy and happy baby. Sometimes these things just happen with no explaination.
I am 25 m/c at 15 weeks and also had a "fluke" pregnancy (a partial molar). I understand your pain and confusion all too well. Feel free to FM me if you ever need to talk.
Feel better soon and here's for when you are ready
I, myself, was the miracle baby born to my parents the year after they lost a baby born prematurely with Down Syndrome. I was born full term and healthy at a whopping 9 pounds and 8 ounces.
I am glad that your genetic counselor was able to give you some good news. This surely gives you something to look forward to.