cramping..

okay so i was cramping really bad the whole week my period was supposed to start even on the exact day it was supposed to start i was cramping soo bad but no period , no spotting, nothing .. it was a little bit on and off but i thought for sure that my period was starting. From what i’ve read i thought implantation was supposed to be a week before the start of your period? im pretty positive that i ovulated late and had implantation cramps the week of my period....i’m just a tad bit confused