Cramping during 2WW??

Hi ladies! Question... I have experienced slight but noticeable cramping on my lower left side on and off for the past 3 days. I am 8DPO today. AF isn't due til 2/18 and these are very different from period cramps. Of course I immediately thought implantation cramping, but if it is implantation cramping would it last for 3 days? Any insight? Thanks!