Sometimes u never know. The only think that was ever found with my two m/cs was low progesterone. I would see an RE. They can sometimes do more advanced testing and have more access to better meds than a regular ob. Good luck to you.
I'm not exactly in the same situation. I have had my son, then two miscarriages in one year and we have been trying to get pregnant since with no luck. It will be a year in June. My blood work I had done said I was perfectly healthy. I also don't drink, smoke, live unhealthy, no drugs. I take a prenatal vitamin everyday and I work out but still no baby, I also had a uterine examine. they put some coloured liquid into my uterious to make sure it was the right shape, no scars from my c-section etc. all perfect. So I have no words of help for you. only that you are not alone. I also do not understand why. I also would like to know how to get pregnant again and have a healthy baby. Idon't have any answers but I want you to know I know how you feel and I'm so sorry you are going through this. Once you have one you want a sibling for that one and you feel so powerless when you keep having miscarriages. so best of luck to you.