I THINK I'M PREGNANT?

I am on the pill (Yasmin) but i have been having unprotected with my Partner and had a OOPS about 2 weeks ago while i was on antibiotics, I am now 3 days late with my menstrual cycle and no signs of menstrual pain, How long should i wait before taking a test??? and what is more lightly Pregnancy OR Mixed up Hormones?????????