I have just a thought...you would have to follow up to see if it applies to you. One relatively unknown cause of infertility is gluten intolerance, also known as celiac disease. There are many documented cases where women removed gluten from their diets and were able to conceive or to stop repeated miscarriages. Unfortunately, this is not something the doctors normally look for. It might be worth a try to avoid gluten and see (even if you don't go through all of the medical testing for celiac). If you do an internet seach, you will find a lot of info on gluten-free diets. Gluten is hidden in many things, so it is not as easy as just avoiding bread products.

Good Luck!