Trying to conceive having pcos and taking metformin, every month i got dark brown blood in start and end of periods is it normal?

Can be normal: The good news is that you are getting a monthly cycle! if you have a day or two of dark spotting right before or at the end of your period that can be normal, as long as the total length is still 7 days or less. Dark just means old. So when the flow is slow, the blood has more time to change color before it comes out. If you have more than 7 days of bleeding, get checked out by your gyn.