Had sex on 7th november, and on 15th I had my period, in which I had clots also, it was a 4-5 days period, after that on 12th december was my next date, but I didn't have period yet, I have tested via prega news on 13th december, the result came negative. The question is why I am not having my periods yet. What could be the reason, when will it happen. I had cramping on 15th, but yet no periods, and worried, is there a chance of pregnancy. But the result came negative, please tell me.