I'm a virgin. But my bf rubbed his penis on my vagina while I was on my pants and he was naked. Is there a possibility to get pregnant?

Fluid transfer ? To get pregnant you need to have a transfer of the semen from his penis into your genitals. If no transfer occurs, you cannot get pregnant. If he had any direct contact with your vagina, by fingers ( with semen ) or penis, even a small amount of semen can do it.