Hello, I Have Been Trying To Convince For About 3

Hello, I have been trying to convince for about 3 1/2 yrs. Recently I was told I had pcos but I receive a period every month. I have had a lot of Test ran and the only thing they found was that my insulin levels were high. I have currently lowered my levels & my Dr put me on metformin twice a day. But I still haven't gotten pregnant. Please help me understand why. Thanks