I had unprotected sex with my boyfriend,he tends to precum a lot and he slid some of his into my vagina, not even two weeks before that I had my period,then two days after we had sex I had my period,it was very light and ended 2 days earlier,I should've had my normal period like last week and it never came,so what coukd this mean?

Sometimes having sex can cause some light bleeding. You should take a pregnancy test if you missed your period's original date. Have safe sex, use a condom and you won't have to worry about pre-ejaculate.