I think that they had sex before they stopped to put the condom on.
kent_low, you would know better than anyone else if there was any sperm involved. I take it that you did not ejaculate until after the condom was on, correct? So you are just worried about sperm getting in before the condom was put on, right?
If there was any sperm leftover from a previous ejaculation, maybe earlier in the day, and you hadn't urinated between that and the sex in your post, she could be pregnant.