Why am I not getting my regular periods after having sex?

Hi doctor,

Before two months, I had protected sex on the 13th day of the cycle, and my partner also ejaculated outside the condom. There was no leakage. I got my regular periods after a month. It started on the expected date and were slightly more massive. They lasted for the average duration, and the bleeding was also usual. But this month, I was waiting for the periods around the same day, but it was about seven days late now. Why am I not getting my second menstrual cycle regularly after having sex? I have white discharge and feeling of periods. But there is no bleeding. Why is it not arriving? I am worried. Can it be an ectopic pregnancy? If it is ectopic, how is it possible to get my periods after intercourse? What will the pregnancy results show now?