Had unprotected sex, took levonorgestrel 2 days later. period is late 6 days and now there is bleeding & it started few bleeding on the 1st day and then it was heavy bleeding on the 2nd and 3rd. is it period or implantation bleeding?

Period more likely: Plan B (levonorgestrel) and other brands of emergency contraceptive pills can alter the menstrual cycle for the cycle in which Plan B was taken, and sometimes the next month's cycle too. One should be sure to check a home urine pregnancy test about 3 weeks after sex, because emergency contraceptive pills work most of the time, but not all the time.