My basic question is...if you have regular menstrual cycles, is there any need to prescribe metformin when trying to conceive? If metformin is prescribed for someone with regular cycles, can it make their cycles irregular?

Brief history:
Three years ago I had trouble conceiving. I was given a pcos diagnosis (because my cycles were about 35 days and I had the "swiss cheese" looking ovaries) and was treated with metformin and clomid which went fine. I became pregnant in a couple of months, but suffered a miscarriage a few months later. A few months after that I became pregnant while just taking metformin. I kept taking metformin until 5 months into pregnancy as well as crinone because I had a progesterone deficiency. I had my son in May of 2013 and he is healthy and happy!

I breast fed for a year and did not have a period during this time. When I stopped breasfeeding I immediately started having regular menstrual cycles...typically 26-31 days in length. I also started getting the "fertile mucus" more noticably.

I had regular cycles for 5 or 6 months. When my husband and I decided to try to conceive again (I'm now 38), I went to my ob gyn and she told me that even though all of my recent bloodwork/hormone levels and ultrasound showed that I was ovulating, that she thought I should still start taking metformin.

I started taking it and all of a sudden I went from normal cycles to starting to spot on the day I should be ovulating. The spotting lasted for 10 days. My ob gyn said that my hormone levels said I was starting a new cycle already! She started me on clomid to get my hormones going again (after the 10 days of bleeding).

After the clomid, I started spotting on day 15 of my cycle again!

Could this be caused by the metformin? She has me on 2 x 750mg a day. The only other thing I do is acupuncture for fertility (which I did with my pregnancy as well).

Could metformin be causing these strange, short cycles? I'm not sure why I need to take it if I have been having normal cycles since my son was born.

Thank you so much for your second opinion on this!
Krista