Hi
This happened to me a few weeks ago. I ended up bleeding for 2 weeks but the doctors wouldnt believe it was the Metformin. I have just had my meds changed to gliclazide and surprise surprise the bleeding stopped!!
I was on the depo injection too, and as you will know that stops you ovulating. The metformin is also used to treat polycystic ovaries and is used to start ovulating so you can imagine how confused your body is feeling!!
My doctors surgery are still saying that the Metformin dis not cause the bleeding but my local pharmacist laughed and said of course its the Metformin.
If I was you, I would ring up your doctors and see if they can change it. One of my worries, was would I still actually be covered if I had sex (not that I wanted to when I was bleeding!!) Also, you dont know what long term damage that could do to your body.
Hope this helps
Louise