Do you think i am pregnant?

me n this guy had sex like three days ago n my cycle came on the next day. my cycle is normally light but it has been lighter than usual. example: sometimes its no blood dwn there n then wen it is its jus a little. i dnt think u can kno tht quickly but we didnt use a condom n he did pull out.(i kno the pullout method doesnt work all the time) but the point is by the description of my cycle cud i kno if im pregnant r not..am i Pregnant? someone plz help n if your going to be ignorant then dnt answer!