Did you do the glucose/insulin tolerance test. Maybe your glucose levels are fine, but your insulin is high, because your body is resistant to it??? and that is why the doctor put you on metformin?
She may have suspected polycystic ovarian syndrome (PCOS) as the reason that you are not having periods.
Metformin is quite a standard treatment for PCOS. If this is the reason you were given metformin I think it would be a good idea to give it a go for at least a few months. I personally know a few women who had great success with regulating their periods on metformin (1 got pregnant on it).
Hope this helps.
WaveRider is correct, and I would do as he suggested.
"She did a standard sugar test which came out as 4.4."
I don't understand why you were diagnosed "insulin resistant" and put on Metformin [Glucophage] as 4.4 mmol/l is considered normal, very normal. I would seek an appointment with an Endocrinologist - a doctor who specializes in diabetes] for a second opinion.