I Had Sex On 4th November And Took I Pill

I had sex on 4th November and took i pill and then on 6th had sex again and then also took pill ,on 15 nov there was little bleeding which went for 2,3 days and was darker in clr and there were dark clots also but they were not proper periods ,on 5th December i did pregnancy test and it was negative and then on 25th December i again did a pregnancy test and it was also negative but there is no sign of periods yet .what to do ?