My friend had 3 or 4 losses in a row and they did a lot of genetic testing. Finally they figured out it was a clotting disorder and she took injectable meds all throughout her next (successful) pregnancy. I hope you can have testing done and find some possible causes.
"Why would you ruin perfectly good peanuts by adding candy corn? That's like saying hey, I have these awesome nachos, guess I better add some dryer lint." - Nonny