Could I be pregnant?

Okay so idk if i could be pregnant or not. My SO pulled out every time except for the 16th of this month but I’m not on my period. Could I be pregnant from pre cum maybe... or got pregnant the day before I was supposed to start? I know if it was from the 16th then a pregnancy test wouldn’t show that soon (it’s been a week). I was supposed to start my period on the 17th of this month. Help.