I had two m/c (d&c's at 13 wks & 10 wks) and another possible m/c before I had my son.
I have a history of thyroid diseases in my family (and just had my thyroid removed due to cancer -oldest is 7).
That is def. the first thing I would have checked.
But in reading all the grief books and looking at the statistics , it is just as likely to have two m/c's as it is to have one.
Unfortunately, they don't get concerned until you have three.
If you do get pregnant and take a baby to term, use the m/c as an "excuse" to get AS MANY ULTRASOUNDS AS POSSIBLE.
That's what I did and it was very reassuring.
You don't say what thyroid problems you have, but your thyroid is one of the most important glands in your body (anybody see the one of the recent episodes of "House"?) It regulates so many systems.
I hope everything works out well for you.
I've been there.
PS - They did give me progesterone pills for my first trimester with my son-I'm sure it was placebo, my first m/c was at 13 weeks-1st week of 2nd trimester, but maybe it did something??? My second son I didn't have any problems with.