My period is 5days late,i had unprotected sex a week ago and i just started spotting,what could be the reasons for this happening?

Can do preg. test: It can be hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. A urine pregnancy test gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. A primary care or an Ob-Gyn doctor can evaluate any persistent or worrisome symptoms.