Confusion regarding period. What is the?

I had sex with husband on 19 of previous month and took i pill within 2 hours of sex. The sperm was not discharged inside the vagina. It was taken out at the time of sperm discharge My period date is 6 of month & on 1 I had period cramps. Next day I spotted black blood clots only one time during day, next day also I spotted blood clots but frequency is more than yesterday and colour of blood clots is lighter than yesterday. I have not diagnosed similar problem ever before. I took urine pregnancy test and it says I  am not pregnant. The colour of blood has changed from  black to red. And whenever I am going to  toilet it is visible at  that time. Currently I am having period cramps  but my period has not arrived. My date of my period has not arrived, it is 6th of the month I am worried about it. Please advise me what is the