Did you already get your first period after giving birth? If so, then this means you are ovulating and could potentially get pregnant if you have sex. Even as uncommon as it is to get pregnant through rubbing-- it is still possible if he ejaculated on or near your vagina. You should be taking your birth control pills for at least two weeks before having unprotected sex or taking a chance with rubbing. I can say that it is not as likely to get pregnant this way as it is it would be if you had sex, but all it takes is one sperm to get you pregnant. Don't stress out about this because stress causes delayed periods and your first few periods after birth may even be irregular. If in doubt you can test for pregnancy one week after your period is due and this will clear up any confusion.
Keep in mind that if you do not want to get pregnant right away-- practice safe sex ALL the time. Your body is much more fertile the first year after giving birth so don't take your chances. :)