Bf rubbed dick on my vagina,peed many times since last masturbation,so no semen in precum.got my period the next day.what are chances i'm pregnant?

Very very low: Any genital to genital contact can in theory result in pregnancy, but the fact your period came the next day makes it very unlikely. Of course it is more responsible to use some type of birth control, or condoms to drastically lessen the chance of pregnancy or catching a sexually transmitted disease.

Nil: If this was a normal,regular period you would ovulate well after 5 days and sperm only survives for no longer than 5 days. Incidentally you can't guarantee that there would be no sperm in precum.