cycle

Ok I have a dumb question. I haven't had time to call my gynecologist, but my cycle has been a little off the past two months. Do any of you mark the start of your period when you see spotting or do you mark the start of your cycle the day you actually see a normal flow? Last month it spotted a couple days before regular flow and this month it did the same too. I was recently put on metformin this month so Idk if that will change anything. Just wondering