Could Delayed Periods With Spotting And Nausea Be Symptoms Of Pregnancy?

Ive always been really irregular with my periods. The last time i had my period eas december 31st. I had unprotected sex on january 12th and then experienced spotting on january 31st which i found weird because that doesnt usually happen to me. It was moderate spotting which i only experienced that night n it was brownish in color n when i wipped it was reddish. So i figured my period was coming that next morning. Well here we are a week later and i have still not gotten my period. These past couple of days ive been feeling nauseous and dizzy so i took a pregnancy test which i figure should be positive by now if i were pregnant but it came back negative. Am i correct in saying if i was pregnant it would come back positive by now?