What Causes Pimples On The Face?

I had my period on Aug. 5, I had sex on Aug. 13. I know the charts say that that was not my fertile time, but I have had nausea and dizziness for the past 4 days and I have this pimple on my face that appeared a day ago and I never have had a problem with acne, someone called it a "pregnancy pimple". Is it possible I could be pregnant?