My age is 28. I want to consult about my periods. I have 3 children one of them have died after 48 hrs of birth. My last period was started on 14november and end 18 november. Now I had a unprotected sex with my husband on 11th december, by keeping in my mind that as per my last period this is the cycle of safe period. But just to clear my doubt I have checked by using preganews kit and test were negative on 12th evening. Again I had sex on 14 and checked by pregnancy kit on 15 evening and test were negative and again test done without having sex on 16 evening and test were again negative. I am ok that test were negative but why period are not happening.