Took Nordette Last April 20 After Having Sex (withdrawal Method)

took nordette last April 20 after having sex (withdrawal method) April 19. I took the first dose (4 pills) then the second dose after 12 hours (4pills). After the second dose, I felt really nauseous but I was able to endure it. After 8 hours, I vomitted a little but I did not see the pills. I did not experience withdrawal bleeding and now my period is already 3 days late. But my period is usually very irregular. Am I pregnant?