2 miscarriages - Unexplained infertility

We're planning for our third pregnancy now since 4 months and I'm not able to conceive even. In my first 2 pregnancies, I conceived in the same month when we planned without any issues. This month we opted for follicular monitoring, and planned everything as per doctor's advice. My period is due in 7 days, and I see symptoms of period now. This is bothering us a lot. My ET was 6mm and after using some medicines it came to 7.9mm before the injection was given for egg release. We don't have any health issues and any family history of miscarriages. I don't know if we are missing something or we're on the right track. We've got done all the tests and everything was absolutely normal. In a YouTube video I heard that there are some microorgans near uterus opening which eat away the sperm and prevent from fertilizing with the egg. And this cannot be detected in any medical tests. Is that true? I'm trying every possible way to find the root cause and fix it. R we missing anything?