Cramps, no period...?

So, my period was due today, the 21st. I'm VERY regular, never late a day in my life. For about a week and a half, I've had cramps. I kept expecting to get my period early but it never came. And then when it was nearing the 21st, I put a pad on just in case...still nothing. Is this normal? And has anyone else ever experienced this? If I haven't got my period in a few days, I'm going to test.