Condom came half off leaving cum on my penis not sure if it happened inside her or after i pulled out i started rubbing on her.chance of pregnancy?

Always: Other than that from an obstetrical standpoint a woman is considered pregnant until proven otherwise there is a slight chance that your lady could have gotten pregnant.

Always a chance!: Even with condoms there is a chance of pregnancy. In this case the chance is increased Plan B, if taken right after (follow instructions), can prevent pregnancy, but it too is not 100% effective. You also, are at risk for STD's when condoms fail to perform properly. Use a back up method of birth control and be sure you and your partner have no std's.