I do not have any advise and I am so sorry that you have miscarried as a result of trisomies, my DD1 has a chromosome abnormalilty and my DD2 has a problem with her heart which they thought was linked to a trisomy, both of these mean a stay in NICU at birth and surgery as an newborn.
Both are random, not linked our genetics passing them on, I am 27 and DH 31 so we shouldn't be high risk, and no other cases in the family.
I know the feeling of not knowing if you will ever concieve a healthy baby and the constant worry even though I have been fortunate to carry to term (at least with DD1 so far).
I am sorry I do not have anything to offer I just hope that you are able to concieve your healthy baby soon.