You might be pregnant. There is something called implantation bleeding that happens in some women. I don't know how heavy the flow can get. Also I have been pregnant twice and both times around the time that I would have been a week or so pregnant I got massive headaches. They kept happening up until the 3rd month or so. I feel like that was my bodies response to all the hormones. Good luck if you're not it's okay there is always next month.