really paranoid about being pregnant. answers?

Hey. I have a scenerio, and i feel really paranoid, even though i did some research. Me and my boyfriend were fooling around, and i was giving him a hand job for a little bit. The only liquid i got on my hands was the pre-cum, since aftera while he wanted to finish it himself. Even then, he did that in a sock, so he didn't even touch the semen. (at least he claims he didn't). then, about 15 minutes after that, he wanted to finger me. however, i first checked myself to make sure i was wet enough, and inserted my finger slightly into my vagina. but the precum that was on my hands was dried out for 14 minutes, and because of that, i completely forgot about it. he then inserted his finger into me for only about two minutes, because we lost track of time and had to leave. i'm always paranoid about this stuff, and i tell myself if i'm so paranoid, not to do it, but it's one of those heat of the moment things. i've been searching around and read different things, like "sperm can only survive in a moist environment. once the semen is gone and dried, the sperm immediately die." and then i've heard that sperm can survive for up to 20 minutes. then another i've heard it dies once it hits air. i'm wondering if anyone can tell me which one is correct, and if it's possible for my DRY HANDS that once had the precum on it could still have live sperm that could impregnate me.