What Causes Dizziness And Nausea After Taking Emergency Contraceptive Pill?

Hi I took the morning after pill after 2 nights unprotected sex (UPS), since then i have been feeling tired, nausea and some times dizzy, this happens any time of the day and it has been 6 days now. I had UPS a week after my periods. I haven't done pregnancy test since i think is too soon to do that. What can it be the problem, is it side effect of the pill or am i pregnant?