Pcos on metformin... getting frustrated/depressed

So, I was diagnosed with pcos when trying to conceive the first time. Doc put me on 2000 mg metformin a day and got pregnant after the 1st month. Now, I'm trying for my second. My new doc only put me on 1000mg. My periods are very regular, 31 days for 3 months, but I'm still not pregnant. I'm not sure if I should ask for a dose increase, since I'm having regular periods. Any advice?