My girlfriend and I have just started being intimate, though we haven't technically had intercourse, I'd rub my penis in and around only the opening of her vagina. I"ve been extremely careful with her and haven't ever ejaculated on or near her vagina, so I haven't been really worried about anything, but recently she's been worrying about being pregnant from my pre-cum, and she's got me to start worrying too. Technically she's still a virgin because her hymen is still intact. I know that even if having penetrative sex, the chances of becoming pregnant from pre-cum are low since there is a very minimal amount of sperm in it, so my question would be, "What would the chances be of her becoming pregnant by pre-cum knowing that we've never had penetrative sex and also that she's still a virgin?"