If you have got your periods within 5 days of unprotected intercourse, it is highly unlikely you could be pregnant. I suppose you are worried that the lighter period is Implantation bleeding and would like to confirm the same. Implantation bleeding occurs in women who are pregnant and is typically a lighter kind of a period that starts 6 - 12 days after the day of fruitful intercourse.
You may take a pregnancy test immediately after missing a period or in your case 2 weeks after the day of the intercourse to be sure that the result is accurate. To take a urine pregnancy test, follow the manufacturer's instructions carefully. It is very important that you note the test result indicators, method of urine collection, etc. as these may change from pack to pack. Most women are able to take the test themselves without any trouble and I am sure you shall be able to do the same too.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.