That does seem to be the ultimate question for a woman as she tries to conceive. Are these symptoms I'm feeling pregnancy related or period related? Hmm.. only time will tell. Unfortunately I'm not a patient person so I've been sitting on pins & needles waiting for my period to come - nothing yet.
Before I ever started taking birth control pills my period functioned like clock work every month, always starting in the morning (what a happy thing to wake up to) and 28 days apart. About every 3 months I would have a short cycle of 24-25 days or a long cycle of 30 or 31 days.