Metformin and fertility

Hello, DH and I are TTC naturally (baby #3) after a successful IVF. I have PCOS and Insulin resistance, my Endo prescribed Metformin to control the insulin problem and she said it will also help my PCOS, therefore will help me conceive "naturally" before trying another IVF...I've been on it for 6 weeks, and already had a period. She said to give it three months (TTC), I was wondering if anyone has had pregnancy success with this medication. I just started monitoring my ovulation and I was also wondering how long are your periods with this med???..Thanks