scared help

i’ve been having unprotected sex lately w my boyfriend and i have sex then give him head after. i’m worried but not worried at the same time of being pregnant. i’m not on birth control and my period is supposed to come in 12 days. i looked up the chances of getting pregnant from pre cum in it said there is a very low chance and that there’s little to no sperm in pre cum. i just need an opinion to ease my mind please and thank you