I need answers

How am I ovulating and still can’t get pregnant. I release an egg each month bc I have my period, but no baby. I do have PCOS and taking Metformin, but still no baby. Been trying for a year. I did get pregnant last July and then had a miscarriage in August, but been trying ever since and still no baby. I need answers. My doctor is telling me I am capable of getting pregnant because I had gotten pregnant before. I need answer.

*My Partner calms he doesn’t have low sperm count.