First of all, how old are you? There can be changes with your period as you get closer to menopause. Or stress itself can reek havok on your whole body and your hormones. And breakthough bleeding is very common in all women. It is caused by the egg being released and the change in homones can make you spot. They even have a name for it. Mezzelsmertz or something like that. And I know that isn't the correct spelling.