My period is late, could I be pregnant?

My boyfriend and I did not have proper intercourse, however our private areas did meet. I was unfortunately not aware pre-ejaculation could contain semen, and of course when I asked him before we did any of that, he said it did not... My period is about 4 days late and we did this about a week and a half ago... Could I be pregnant? (I am 17 and naive about sex in general, and I know I shouldn't have been doing this so carelessly, please try to ignore my poor, momentary lapse in judgment and try to help me. Thank you.)