First, I am so sorry to hear what you're going through. I just experienced my 2nd mc in a row, too, and have been asking the same thing.
I am finding it is difficult to know whether or not to believe a theory one healthcare provider has over another...basically, at this point, no one knows for sure. Of course it will be great to hear there is a specific reason why both mc happened and there is a fix for it. Hopefully you will get answers.
My suggestions, if you're open to them, are to find a healthcare provider who will do some testing for you. My OB ordered the blood panels for the clotting and lupus. I'm also going to a repro specialist to do more blood testing. They said because I've had two in a row and I'm 36 they'd do it. I guess it depends on your insurance too. Also, start taking a baby aspirin a day; if you have an issue related to clotting this can help and it won't hurt if you don't have a problem. Last suggestion on the practical front, consider working with an acupunturist, if that is an option. The only "condition" the AMA endorses acupunture for is infertility and related issues.
On an emotional note, I started to see a therapist who is reminding me it is important to work through the emotional stuff, too, not just "figure it out". She suggested I find a way to honor and acknowledge the losses. It's great to talk with someone who is willing to listen and sit with me through the tears that I still have.
Thanks for sharing.