Metformin: how long until periods should start happening?

[Beaverfeaver2]

I have been prescribed metformin and have worked up to a 2000mg dosage daily.

I still have no sign of AF.
It's been over 3 months since my last AF which was only really light spotting that lasted 2 days

It didnt work for me at all. I took it for 6 months and didnt have a single spot. I think it works for some and not others