Metformin spotting for 2 weeks?

Hey ladies, I have PCOS and have been TTC for nearly 3 years now. Since 3 years ago, I havevery very rarely gotten a period naturally, maybe 2 times. Usually the docotr prescribes me primolut and then clomid. Anyways, I started taking 1700 mg of Metformin two weeks ago and ever since the second day on it, I've had spotting every single day. Not a period, just spotting. I'm relieved that it has some affect so hopefully it will help me but I don't know if this is normal. I hope someone can shed some light for me because I am a bit worried