Hi, I had sex with my boyfriend just before 4 days of periods. But unfortunately I did not get my periods yet. Its been 9 days we had sex nd 5 days delay of my periods. I'm 100% sure that I'm not pregnant because we used condom very effectively. I observed the same situation previously in my periods delay when we have sex just before they start. Otherwise it is regular every month. Why is it happening. Can someone help me out to understand.