Please help...

Hey people...i need help...m now 18 n i had intercourse n we used condom but we had it on day when there were 33% risk for pregnancy... n now m 2 days late...but i had my exams since last 20 days...so i had lot of stress n longer working hours...m worried that if i am pregnant...plzzz suggest me...i had the home made pregnancy test with sugar n detergent...the test with sugar was negative...but m not sure about the test with detergent...what should i do..??plzz help...