Anyone else had this happen when on Metaformin?

💖😎💟 • I want to be a Mommy!👶 I believe in the good of humankind. 💕
Since I went on Metaformin I've had periods of 3 days of spotting, one day of moderate bleeding, and another 5 days of spotting, for a total of 9 days. I'm worried that I'm not building up that blood lining in my uterus, so if the egg and sperm met there wouldn't be enough of that lining for it to implant itself and continue on into a healthy pregnancy. Has anyone else had this happen?