Late Period after Unprotected Sex

Women may undergo variations in the menstrual cycle but if you are experiencing periods after a short time it is an indication of some other underlying problem. For further evaluation and diagnosis, I would suggest consulting a gynecologist. They will be able to administer treatments that are specifically tailored for your condition.

Missed periods could indicate various possibilities, including pregnancy. Spotting a week before your expected period could be an early sign of pregnancy, but it's also important to consider other factors that might be causing the delay. Take a pregnancy test for confirmation

If you miss a period for more than 3 days, it may be implantation bleeding as well as a medical condition. A gynecologist should be consulted for a thorough examination and diagnosis. The gynecologist or an obstetrician is the best consultant on such conditions.
 

If you used a condom that didn't break or leak and you had sex on the 8th day of your cycle, there is a low chance of getting pregnant. It's usually difficult to conceive at such times in the menstrual calendar. However, remember that no contraceptive is entirely foolproof although using it correctly reduces the risk significantly. If there are any unusual signs or symptoms, it may be a good idea to do a pregnancy test to be sure.

Sometimes the home pregnancy kits show incorrect result. Or may be you have other health conditions. Talk tour gynecologist to confirm