Hi J..
I'm so sorry to hear about your miscarriages. I know how devastating they can be as I've had two myself. My situation is a little different than yours but I thought that sharing could help? You never know...
Both of my miscarriages occurred at around 8 weeks when the fetus simply died and not having any symptoms of miscarriage, I didn't find out until the ultrasounds. I had a hysteroscopy as well and several blood tests with no negative findings. So, when I was ready to try again, my doctor gave me a prescription for progesterone suppositories to take a few days after I ovulated and continue taking once I found out that I was pregnant. I don't know if that is what finally worked but I have a 7.5 week old, a healthy beautiful girl sleeping in her bassinet as I write this.
I didn't have trouble conceiving either I guess I just needed some extra progesterone help to keep the pregnancy. I only had to take the suppositories for 8 weeks until we knew that our baby was healthy.
I hope that this helped. I would ask your doctor about progesterone. Although it's not proven to work per se and the evidence is inconclusive, it seems to have worked for me.
Good luck.
P.