What Are The Chances Of Pregnancy Having PCOs?

I have pcos and have been on metformin for 2 months now. 500mg 3 times daily. I was on this same does for 6 months last year and I still have not been able to conceive, however I have noticed that both times I was on this medication I get a vaginal smell of garlic. I have been in a monogamous relationship for three years. I have been tested for every std and infection possible and they all came back negative. I am wondering why this is happening and also, if there is a way to prevent or treat it? thank you so much for any input.