So, I started Metformin on 2-1-08 and haven't gotten a period but that isn't really a surprise. Metformin itself wouldn't actually give you a period on it's own. If you are insulin resistant, then that can affect your hormones which can keep you from ovulating. The idea of Metformin is that is corrects your insulin levels which can "unlock" you ovaries and allow you to ovulate. (This is what my doctor told me.)
If Metformin doesn't help your cycles, you will probably need to go on Provera and/or Clomid which does cause you to ovulate. (That is it's actual job. LOL)
I have no idea if this helps or ever makes sense but good luck TTC!!!