menstrualhut

Now, I've been getting my period for 7 days, no less, since the 2nd period I ever got (the first one was 3 days). I'm never late, never missed one, nothing. I'm on Ortho-tri-cyclin, but it's never had an effect on my period in the 3 years I've taken it.
And this month, for some reason, my period stopped after 4 days.
I'm not *super* worried I'm pregnant, as I am on the pill, and he never ejaculates inside me (either we use a condom or he pulls out), and I did bleed pretty darn good for at least one day (as in, soaking a regular tampon in an hour). But, of course, you hear stories about women getting pregnant while on the pill and using condoms and still getting their periods.
I haven't changed a whole lot. I started exercising a bit more, but not that much. I also haven't been getting a lot of sleep (4-5 hours a night). I also had weird cramps a few days before. They felt more like intestinal cramps than menstrual cramps (though, those came right on time).
Do I have anything to worry about? Has something similar happened to any of you?
Thanks!