metformin and bleeding

I started metformin a little over a week ago. I'm on 500mg a day. I was put on it because my cycles are long. I've had the usual stomach issues that accompany it and migraines but today i started bleeding heavy out of nowhere. Strange because I had a period 2 weeks ago and my cycles are usually 6-7 weeks long. Does the metformin cause bleeding like this? I've searched the Internet and can't find much on it. Thanks!!