When starting metformin start slowly as they can lead to gastro upsets. I started with half a tablet with breakfast for a couple of weeks, then added the other half with dinner and gradually built up to 2 a day, Gyno recently added another tablet. I've also been on clomid on the past, but doesn't seem to work with me (i ovulate but nothing else happens) and like AJC got headaches but they aren't too bad. If you do fall pg, it's all worth it, isn't it? Clomid has a low risk of multiples, but I always think, if they're going to happen, they will anyway. My gyno also advises you to stay on metformin if you fall pg, but talk to your own gyno about that one as there are risks.