i had unprotected sex on 8th, 12th n 14th feb... and now im bleeding from 3 days, first day was usual like periods but then slow down... usually 2nd day is the heaviest for me, but i only have spotting on that day n now its just if i wipe i have blood, i was supposed to have periods on 27 feb , could this be implantation bleeding, is this usual to have it for 3 or more days??