I held the boxers of my bf wd precum. I applied alcohol after 30 min and changed my napkin coz I was having my period. Will I be pregnant?

Highly unlikely . It is highly unlikely that you would get pregnant by just holding your boyfriend's boxer shorts in your hand regardless of the fact that they had semen on them especially whole on your period but it sounds like it's time for you to discuss starting a reliable method of contraception so that you don't have to worry and don't forget the condoms to decrease the risk of STDS. Hope this helps.Be safe.