Have you tried counting calories? I know that for many women with PCOS a low carb diet really helps with weight loss, but for me as long as I stick with around 1500 calories a day of healthy food (which includes fruits, some dairy, and sometimes starches) I still lose weight. Calorie counting is usually a good place to start, and I've found that keeping a food journal where I write down what and how many calories I eat is very helpful. Even if you don't start dropping calories straight away, a few days of journaling can give you a better understanding of your intake, and from there you can decide how to modify it.
As far as the Metformin goes, I empathize. I was on 1000mg per day for a month, and I could hardly leave my house, I was so sick. In the end I had to stop taking it, but my hormone levels normalized themselves with just birth control pills. Many other symptoms of PCOS decrease for me as I lose weight as well (my periods become regular without the help of medication, for instance).
Feel free to send me a private message, if you want to talk in more detail