Re: What's the next step if metformin doesn't work?
Why did your doctor put you on metformin to start your period? It's a diabetic drug to assist with insulin stabilisation. It's usually given to women with PCOS to assist in stabilising insulin to assist in weight loss. You are at a healthy weight so I don't see why you need it.
There's a couple of things you can do. First of all, you can look at your diet. A diet high in starchy carbs (sugar, bread, wheat, potato, rice, pasta, etc) can create problems if you have insulin resistence as the body reads all these things as basically sugar. You can try removing them for a while and see if there's any effect. I'd suggest at least 2 months to allow the body time to adjust.
You can also think about going to a naturopath or Traditional Chinese doctor to see about some alternative treatments. We have an acupuncturist near us who has had extremely good results helping women with fertility issues.
Another thing you can do is go on the pill. This will create an artificial regular period for you, which is fine for now, but you will need to look into fertility later on if/when you decide you want children.