Cramping before period?

How long do you guys normally cramp before your periods? I have been cramping for 3-4 days and no period yet, took two HPT but both negative. So it may either be to early or this may be an issue of coming off the pill on the 16th of July and my body regulating. I know when I was pregnant with my first cramping was my first sign. This time I'm not sure since too negative tests, so is it normal to cramp for awhile before the flow starts?