Pcos metformin and confused..


So I have been on metformin for about 6 months now. I take it at night because it makes me so sick during the day. I have not had success with getting pregnant but my periods have been very regular since I started taking it. Well this month i was 8 days early (which has NEVER happened) and it was brown for 4 days and then just stopped. And very light. Has anyone else had this happen ?